Gas in Cold Weather: The Myth of "Fractioning"

I'd like to dispel a myth that's out there: the myth of "fractioning."

Supposedly, if you've got a typical canister of gas (i.e. containing propane and some form of butane), in cold weather (temps below the vaporization point of all but the propane), only that fraction of the fuel that is propane will burn. Supposedly.

Here's an example of the myth: You have a canister that is 70/30 butane/propane. Propane vaporizes at -44F/-42C; butane at +31F/-0.5C. Now, say it's 20F/-7C out. According to the myth, only 30% (that fraction of the mix that is propane) will burn off.

That's the myth.  What really happens?  Well, take a 70/30 canister out in 20F/-7C weather and burn it until it's empty. Now weight it. You'll find the weight is lower than if only 30% of the fuel had burned off.

Why? Well, when you mix liquid hydrocarbons, they combine to form a blend. The blend has properties that lie "between" the properties of the constituent fuels. For example, the boiling point of a 70/30 blend of propane and butane will have a boiling point between -44F/-42C and +31F/-0.5C. The math is non-trivial, but if you know the formulae, you can calculate the resultant boiling point. In this case, a 70/30 blend has a boiling point of about 0F at standard pressure (1 atmosphere/1013mBar).

Now there is a little bit of a catch to all this. This "blend" of liquid hydrocarbons in a canister of gas (recall that there's so much pressure inside a cansiter that our gasses liquefy) still has two distinct molecules in it: Propane molecules (C3H8) and butane molecules (C4H10). The propane molecules have a higher vapor pressure than the butane molecules. In other words, the propane molecules tend to vaporize more than the butane molecules in the blend. How does a canister typically work? Well, you draw vapor off the top, and then more of the liquid portion of the fuel vaporizes to replace the drawn off vapor. If the propane is what most readily vaporizes, then the propane will be removed from the blend more rapidly than the butane. This is called "preferential" vaporization. Because the propane is vaporizing faster than the butane, your blend will change over time as the canister empties.  As the blend changes, so will the vaporization point.  Toward the end of the life of the cansiter, all the propane will be gone and only your secondary fuel will remain.

Uh, isn't this "preferential" vaporization the same as "fractioning?"

No, not at all. Remember that the myth of fractioning calls for only the propane to burn leaving behind all of the butane. What happens in reality is that the blend vaporizes some butane and some propane throughout the life of the canister until the propane is gone. Yes, you will reach a point where all of the propane is gone and only butane remains, but the fact of the matter is that you will be burning off far more fuel than if only propane alone were burning.

With fractioning (if it were true), you could only burn of 30% of the fuel in a 70/30 canister. With preferential burning, you burn more like 75% of your fuel before you wind up with nothing but butane left (the actual amount burned varies with altitude and temperature of course).

This brings up two important points:
1. Don't use canisters with regular butane in cold weather. Eventually all your propane will burn off, leaving behind whatever else is in your canister. If you've got isobutane (vaporizes at +11F/-12C) as your secondary fuel you've got a 20F (10C) degree advantage over a canister that has regular butane (vaporizes at +31F/-0.5C) as its secondary fuel.

2. Stoves that can handle running with the canister upside down (inverted canister stoves) draw fuel off the bottom of the canister. If you're drawing fuel off the bottom, you're only drawing liquid. If you're not drawing vapor, then it doesn't matter which fuel vaporizes at what rate. Inverted canister stoves start and end with the same fuel blend. If you start with 70/30, you end with 70/30, and your vaporization point stays low, allowing you to run your stove in much colder weather than a conventional upright (screws onto the top of the canister) gas stove. With an inverted canister stove, you can burn all of your fuel in cold weather (assuming that your blend's vaporization point is sufficiently high for the weather).

So, there you have it: What's really going on in that canister of yours in cold weather. I hope this puts the myth of "fractioning" to bed.

I thank you all for joining me on another Adventure in Stoving,

HJ

Related articles and posts:

• Cold Weather Tips for Gas Stoves
• What's the Best Gas for Cold Weather?
• Canisters, Cold, and Altitude:  Gas in a Nutshell
• Gas in Cold Weather:  The Myth of "Fractioning"
• Canister Stoves 101:  Thread Care
• Gas Blends and Cold Weather Performance.  (Why not just use propane?)
• Gas Stoves: How Cold Can I Go?
• The "SuperGnat"  (Camping Gaz or threaded canisters with one lightweight stove)
• Backpacking Gas Canisters 101    
• Gas in Extreme Cold:  Yes or No?
• Stoves For Cold Weather I (Upright canister stoves) -- Seattle Backpacker's Magazine
• Stoves for Cold Weather II (Inverted canister stoves) -- Seattle Backpacker's Magazine

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What's the Best Brand of Gas for Cold Weather?

For warm weather use (above 50F/10C), it doesn't much matter what brand of gas you buy.

For cold weather use, the brand of gas you buy does make a difference.  Typically, gas canisters contain some blend of propane mixed with either "regular" butane (n-butane) or isobutane. Some canister brands contain all three gasses.  For cold weather use, you generally want a canister with as little n-butane as possible.  Even though propane is the best cold weather gas, I'd take a canister with 10% propane and 90% isobutane over a canister with 30% propane and 70% n-butane.  Why?  Because the propane will burn off at a faster rate than the n-butane, leaving you with nothing but n-butane toward the end of your canister.  Butane is a poor performer in cold weather.

Why is butane a poor cold weather performer?  Why do we use blended gas?  Why don't we just use 100% propane?  That's all covered in my post on Gas Blends and Cold Weather Performance.

What companies have got the best blend?  I don't have all the data, but here below is what I have.  This data is for the United States of America.  Brands and blends available elsewhere may vary. 
GOOD WINTER GAS BRANDS (in no particular order)

• MSR is a good winter blend, 80% isobutane and 20% propane.  These numbers are confirmed on MSR's website.

• Brunton is reputedly made by the same Korean company that makes MSR canisters and is said to have the same blend (80/20).  I have not been able to confirm these numbers.

• Jetboil is also supposedly 80% isobutane and 20% propane.  I have not been able to confirm these numbers.

• Snow Peak is 85% isobutane and 15% propane.  These numbers are confirmed on Snow Peak's website.

• Coleman Powermax is 65% regular butane and 35% propane.  These numbers are confirmed on Coleman's website.  Note:  This is for Coleman Powermax fuel only and is not for Coleman's regular gas canisters.  I wouldn't normally recommend a fuel containing regular butane for winter use, but Coleman Powermax is used in liquid feed mode, so the butane doesn't hurt anything.  Indeed, Coleman Powermax fuel is the best winter capable gas blend available in the United States.  Only the following three Coleman backpacking stoves can use Powermax fuel:  the Xpert, the Xtreme, and the Xpedition.  Update on Powermax 07 Nov 2011.

BRANDS NOT RECOMMENDED* FOR WINTER USE (in no particular order)

• Coleman regular threaded canisters (not Powermax) are 30% propane and 70% butane.  These numbers on on the side of the canister.

• Primus is 25 % propane, 25 % isobutane, and 50 % butane per their website.  I suppose it's better than Coleman brand, but I'd still rather have a fuel with no regular butane at all.

• Optimus brand is 25% propane, 75% butane, as printed on the side of the canister.  Since it contains regular butane, I wouldn't use it in cold weather.

• Glowmaster is 20% propane and 80% butane per the side of the canister. 

One caveat to the above:  If you're using standard threaded canisters in liquid feed mode (in other words, the canister is used upside down) or you're using a canister that is designed for liquid feed (e.g. a Powermax canister), the component gasses are less relevant.  In liquid feed mode, the liquefied gas stays blended and all of the fuels burn together at a constant rate.  With liquid feed, the propane does not burn off more quickly, and you're not left holding the bag with nothing but crappy (in cold weather) butane left.  In other words, with liquid feed, "regular" butane isn't such a bad thing provided that you've got plenty of propane content.

For "normal" (canister right side up) use, avoid "regular" butane for cold weather.

HJ

*Because they contain "regular" butane, a very poor fuel in cold weather.

Related articles and posts:

• Cold Weather Tips for Gas Stoves
• What's the Best Gas for Cold Weather?
• Canisters, Cold, and Altitude:  Gas in a Nutshell
• Gas in Cold Weather:  The Myth of "Fractioning"
• Canister Stoves 101:  Thread Care
• Gas Blends and Cold Weather Performance.  (Why not just use propane?)
• Gas Stoves: How Cold Can I Go?
• The "SuperGnat"  (Camping Gaz or threaded canisters with one lightweight stove)
• Backpacking Gas Canisters 101    
• Gas in Extreme Cold:  Yes or No?
• Stoves For Cold Weather I (Upright canister stoves) -- Seattle Backpacker's Magazine
• Stoves for Cold Weather II (Inverted canister stoves) -- Seattle Backpacker's Magazine

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MSR Whisperlite Universal -- First Videos, Detailed Photos

I'm in the process of writing a review of the new MSR Whisperlite Universal stove.


UPDATED 10/4/2011:  I have written a review of the MSR Whisperlite Universal.

See also this related post which contains additional info on the new (for 2012) stoves from MSR.

The new MSR Whisperlite Universal

I'm still working on the review, but I've posted some rough videos. Don't be expecting slick production values, but if you're interested in the stove, these videos should be pretty informative.

MSR Whisperlite Universal -- First Look







Field trial: MSR Whisperlite Universal, running on canister gas.





Another video of running the MSR Whisperlite Universal on canister gas.





The MSR Whisperlite Universal -- changing from liquid fuel to canister gas:





MSR Whisperlite Universal -- Flip Stop:





I've also posted some detailed photos -- and commentary:






I'll have more to say after I get the stove out in the field, but I thought I'd give you some preliminary thoughts now.

HJ

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How Much Gas Do I Have Left?

It’s day five of my seven day trip. I still have a couple of days of cooking left to do. If I run out of gas, I’ll be eating uncooked freeze dried meals (yuck!). Can I afford to make my morning coffee? Just how much stinkin’ gas do I have left!?

I've got an article in Seattle Backpacker's Magazine on just that very subject.

HJ

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Why a Gas Stove?

I recently got a note from "DG" concerning what type of stove is best:

I vote for liquid fuel type stoves. Fast heat no matter what condition.
--DG

I don't disklike liquid fueled stoves the least bit, but I thought I'd talk a little about why I also like gas stoves.  Read on...

DG,

My first stove that was all my own (i.e. not my dad's) was an MSR Whisperlite that I bought in 1987. It's still going strong.

You're absolutely right that a liquid fueled stove will work in all conditions. But let me list out a few reasons that people might want to also have a gas stove on hand:
1. Bulk and weight. A liquid fueled stove typically takes a fair amount of room in the pack as does the fuel bottle. I can literally hold a little gas stove in the palm of my hand.

Optimus Crux

And in no way is a liquid fueled stove anywhere near as light as a gas stove.

2. Speed. I've been using liquid fueled stoves for years. My family used them back in the 60's and 70's when I was a kid, and I've been using them on my own since the 80's. I've got priming and set up down to a science. HOWEVER, even if you're good at set up and priming, it takes time. I started noticing that my friends were getting tired of waiting for me when we were breaking camp. I bought my first gas stove just so I could break camp as quickly as my friends.

3. Cost. You can go on down to Walmart and get an inexpensive Coleman gas stove for something on the order of $30.00. The cheapest white gas stove is at least double that. The cheapest decent white gas stove is probably another $10 to $20 more expensive than that. The cheapest decent multi-fueled (white gas or kerosene) is at least $10 over that.  Over time, a liquid fueled stove may prove cheaper -- if you stick with it. For those just trying out backpacking or who aren't going to do a lot of backpacking over time, the gas stove will be significantly less expensive.

So there you have it: Gas stoves are lighter, faster/more convenient, more compact, and less expensive than liquid fueled stoves. They're great for fair weather hikers or as a supplement to four season hikers.

All that said, I continue to use white gas as my primary stove fuel. But on those trips where the weather will be good and I want to go fast and light, gas is my choice.

HJ

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Stove of the Week: MSR Rapidfire

OK, so this week's stove is a bit of a "sleeper" in the sense that it's not a stove that you would expect a lot from -- unless you knew better.  But you'll have to read on to find out what's so interesting about this week's stove, the MSR Rapidfire.

First, let's go through our usual run down of the stove, and then we'll get into some of it's unusual qualities.  So, what's with this thing called a Rapidfire?  Isn't it just a Whisperlite?  I mean seriously, just look at it.  It's a freakin' Whisperlite for crying out loud.

Or is it?  Take a look at the bottom of the burner column.  Hmm.  No priming cup.  OK, so what the Dickens is this thing?  Well, it is a close relative of the Whisperlite all right, but made to run on canister gas.

The Rapidfire was MSR's first entry into the gas stove market.  Prior to the Rapidfire, MSR was a liquid fuel only stove manufacturer.  When MSR saw how gas stoves were really catching on, they needed an entrant into the market.  How better to get there than to simply modify their existing "workhorse" stove, the Whisperlite?  Enter the Rapidfire.  Apparently, MSR was pretty paranoid about the volatility of gas as compared to liquid fuel; they really lengthened the fuel line which is odd when you consider that now the majority of MSR gas stoves mount directly on to the canister.

The stove itself is identical to the Whisperltie except for the aforementioned lack of a priming cup.

Instead of a priming cup, there's a threaded, knurled ring that holds the fuel line and legs in place.

At the end of the fuel line, there's a gas connector and valve rather than the open ended tube with aluminum block and catch-arm of the Whisperlite.

Now take a careful look at that connector.

Note the central pin.  It is this pin that depresses the Lindal valve inside the canister of gas.  I've seen these pins go missing.  No pin, and essentially you've got no gas.  Second, note the black rubber "O" ring.  This "O" ring must be in place for you to operate the stove safely.  Without the "O" ring, gas may leak which could be quite dangerous.

Speaking of gas, it's worth mentioning here that the MSR Rapidfire stove can use any standard threaded backpacking gas canister.  Originally, the Rapidfire used a cylindrical gas canister, but that canister had the same 7/16" UNEF standard thread as used on today's dome shaped canisters, so there's no problem with respect to finding fuel even though the Rapidfire is an older stove.  MSR discontinued production, to the best of my ability to discern, in 2001.

OK, so MSR needed a gas stove, so they pressed a modified Whisperlite into service, so what?  I mean does this Rapidfire have any redeeming features or is it just some kludgey attempt to not let all the other stove manufacturers run away with the gas stove part of the stove market?  Actually, the Rapidfire has several features that distinguish it from typical gas stoves, one of which actually makes the Rapidfire potentially pretty worth owning.  I'll get to that in a moment.
First, the Rapidfire, like its progenitor the Whisperlite, is a remote fueled stove.  In other words, the fuel is not directly attached to the burner but rather fuel is brought in via a fuel line from a remote source.  This does several things for us:  1) since there's no fuel tank under the burner, the burner is lower which brings us out of the wind.  2)  Also since the burner is lower, the stove is more stable.  3) Lastly and most importantly, since the fuel isn't local to the burner, we do not have to worry about heat radiating from the burner and overheating the fuel -- which means we can use a windscreen with complete impunity.  Use a windscreen the wrong way on a typical canister stove, and you could turn your stove from a domestic servant into a domestic terrorist.  Overheated canisters can and do explode.

Speaking of windscreens, here's a Rapidfire all set up with a heat reflector and windscreen, a very efficient cooking set up.

Now, I keep blathering about something special about the Rapidfire.  Let's take a closer look at the burner itself shall we?

Do you see that loop in the burner?  That's the fuel line.  That loop is referred to as a pre-heat loop (or generator).  The loop is exposed directly to the flame when the stove is in operation.  Fuel flows into that loop before it enters the burner, which greatly heats the fuel.  In a liquid fueled stove, that heat is what turns the liquid into a vapor so that it can be burned.

Well, that's just great, Jim, but we're working with gas here, so who really cares?

Are you?  Really?  Pick up a full canister of gas and shake it.  Hear that sloshing sound?  That's a liquid in there.

OK, great, it's a liquid in the can but it's a gas when it comes out of the burner, so I still don't care about that pre-heat loop; can we just move on?

Well, not so fast there.  Yes, you're right, it is a gas when it comes out of the burner.  Usually.  But what about cold weather?  Gotcha.  That's the problem with gas stoves.  They lose power when the weather gets below freezing because the liquefied gas in the canister won't vaporize properly.  Remember that pre-heat loop?  There's our answer.  In cold weather, we let the liquefied gas stay liquid, and we let the pre-heat loop vaporize it for us.  In that way, we don't care if it's cold or not.  We don't use the air temperature to vaporize our gas, we use the heat of the flame.

Uh, great Jim, but the connector attaches to the top of the canister, and all it's going to draw is gas off the top.  If there's no gas, we've got no fuel.

This is not a problem.  Just turn the canister over.  Note:  Do not invert the canister on a gas stove that does not have a pre-heat loop.  A serious flare up might result. 

The top of the canister is now the bottom.  That portion of the fuel that is in vapor form now acts to pressurize the canister, pushing liquid down, out of the canister, and down the fuel line.  The fuel stays in liquid form until it hits the pre-heat loop where the high heat causes it to change from liquid to gas.  The resultant gas comes rushing out of the burner, and baby you've got flame.  Note that the stove is in operation in the above photo.  When gas is fed in liquid form to the burner, the stove is said to be in liquid feed mode.  Note that I said liquid feed not liquid fuel.  The fuel will still be a gas at room temperature and pressure.  We haven't changed fuel; we've merely changed the form that the fuel is fed in.

Using a gas stove in liquid feed mode is an important capability for a couple of reasons:
1.  Normal gas stoves operate in vapor feed mode, that is the fuel is fed in as a vapor, and you have to rely on the ambient temperature to vaporize your fuel.  In liquid feed mode, you rely not on the outside temperature but on the heat of the flame.  Stoves in liquid feed mode will operate in colder weather than normal gas stoves.
2.  In normal gas stoves, the fuel is typically a propane-butane or propane-isobutane blend.  Propane, the gas that works best in cold, has a higher vapor pressure and burns off faster leaving you, toward the end of the life of the tank, with a tank full of your worst performing cold weather fuel. In fact, you may wind up with a canister that is still 30% full that you can't coax any gas out of because all the good propane has burned off and nothing is left but the lesser performing fuels.  In liquid feed mode, all the fuels are burned at a constant rate.  The fuel towards the end of the life of the canister is the same mix as at the start of the canister.  In liquid feed mode, you don't get such horrible "canister fade" like you do in vapor feed mode.

I normally recommend a cut off of about 20F/-7C for normal gas stoves -- and that's with using "tricks," having to put up with less-than-stellar performance, and potentially having fuel that you can't get to vaporize.  With a gas stove in liquid feed mode, you can easily go down to 0F/-18C without having to use a lot of tricks, with full performance, and without having a portion of your fuel being unusable.

In other words, with a gas stove in liquid mode, you get all of the convenience of gas without all the low performance and hassles associated with gas in cold weather.  Uh, couldn't I just use a regular liquid fueled stove?  Sure.  If you're comfortable with liquid fuel, go for it.  But consider this:  If it's really snowing hard and you need to cook inside your tent do you really want to use liquid fuel?  What happens if your priming gets a little out of hand?  With a gas stove in liquid feed mode, you get liquid fuel performance but without the danger of priming.  And of course you get all of the usual convenience of a gas stove.  One of those conveniences is simmering.  It's pretty tough to get the typical Whisperlite to simmer like this:

And that's without monkeying around with only filling the fuel bottle half full and only pumping a few strokes.  Easy, just about automatic simmering in other words.

Now, in all fairness, other remote canister gas stoves have pre-heat loops. Other remote canister stoves can operate in liquid feed mode.  What makes the Rapidfire a "sleeper" -- a stove you wouldn't expect much from but turns out to be a pretty good stove?  Well, take a look at the price tags on some of those stoves out there that are remote canister stoves and have pre-heat loops.  They're expensive.  The Rapidfire is an older, discontinued stove, most people haven't heard of it, and you can pick one up for a much more reasonable price than you can some of the current production stoves.  All the performance at a fraction of the price.  You heard it here on Adventures in Stoving.  :)  Also, the Rapidfire's fuel line rotates easily at the connector which makes it easy to invert the canister to put the stove into liquid feed mode.  The Rapidfire's more modern cousin, the Windpro, does not rotate easily at the connector.

Yep, the Rapidfire is a "sleeper," but don't underestimate this stove.  It's a lot of stove for the money.

Well, looks like the kettle's boiling.  I'd best get to that cup of hot chocolate before it gets cold.

Thanks for joining me on another Adventure in Stoving.

HJ

The MSR Rapidfire
What's good about it?
Able to operate in liquid feed mode
Economical
Can use a full windscreen with impunity even though it's a gas stove
Simmers well
Connector rotates easily for liquid feed mode
Quiet
Fairly compact
Reasonably powerful
Reliable
Stable
Efficient

What's bad about it?
The wire pot supports are difficult to get back into "true" if they get bent.  (so don't bend them!)
The fuel line is a little stiff particularly when compared to newer stoves like the WindPro.
A tad heavy when compared to newer stoves like the WindPro.

Overall, recommended.

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Stove of the Week: MSR Reactor

Sometimes, technology can be brought to bear in ways that change the very game.  So it is with the technology of the MSR Reactor.

Hail the inferno; this is the hottest stove out there.  It boils water faster than anything else I've ever seen.  It's not light, it's not cheap, but dang is it effective.

Let's take a look.  Here's a Reactor all packed for travel. The handle locks across the clear lid holding everything securely.

Inside you can fit an 8oz/230g canister of gas, the burner, and a little bit more.  I've got it wrapped here in a wash cloth just to prevent rattling.  It could easily accommodate a spoon and a lighter.  One pushes the "ball" on the left side of the handle.  The handle springs up.  One then unfolds the handle, like so:

I like the fact that the handle locks down, holding everything in place, but herein lies a vulnerability.  The small piece of metal shown below is all that holds that handle in place.

Every time that handle is folded or unfolded, that small piece of metal has to bend.  Repetitive bending of a metal = metal fatigue = failure.  I've not heard of failures of this point, but they inevitably will come.  How soon?  I can't say, but I think this is a weakness in the design.  Note:  I don't mean to sound alarmist here.  I don't think the handle will fail immediately. I think we're talking about years here not days or months. 

Another nice feature, the burner nestles up inside a 8oz/230g sized gas canister.

OK, so it packs up nicely.  Fine.  But what the Dickens is all the buzz about?  I'll tell you.  HEAT, baby, heat.
The MSR Reactor is all about putting heat into whatever is in your pot.  How does it do it?  First, with a radiant heat burner.  It burns fuel, but not in an open flame like a normal burner.  Instead, the burner head is heated by the burning of gas and then heat is radiated into the pot.  The radiant heat burner:

Heat is transferred first by a fairly tight nesting of the burner underneath the pot.

And then by an integral heat exchanger

Wind?  Not a problem.  When the pot is mounted on the burner, you can't even see the burner.

Heat flows from the burner to the heat exchanger into the pot.  Any exhaust heat is forced up along the sides of the pot until it reaches the vents seen in the above photo, a process transferring yet even more heat to the contents of your pot while still being almost totally protected from the wind.  In a 100 mph gale on top of an exposed plateau at 15,000' (4500m), this is the stove to have.  Note also that I'm holding the burner at a steep angle.  The pot doesn't budge. If you jostle your pot in tight quarters, no problem.  Your pot -- and your supper -- are staying right where you put them.  No tippy, slidey action here.  Still, not a bad idea to put a set of "legs" under your canister if you've got 'em.  The Brunton CanStand, Primus Foot Rest, and JetBoil tripod stabilizer all should fit an 8oz/230g sized canister.  The JetBoil version is shown here.

Another nice feature?  How about liquid measurement lines on the inside of the pot?

And don't forget the little pack towel they give you.  I use it to protect the bottom of the burner -- and the bottom of the pot.

One caution:  This is a seriously hot stove.  A friend of mine walked away for a minute and got distracted.  When he got back, the pot had not only boiled dry, it had melted.  It's a dang good thing that his canister didn't overheat and explode.  As it was, he lost his pot.  He could have lost a whole lot more.  This is a stove that you want to keep an eye on.

Well how about at the other end of the temperature range?  What about simmering? Well, the Reactor quite frankly has a bad reputation in the simmering department.  But lack of simmering is not a given with the Reactor.  There are a lot of individual variations Reactor to Reactor, and some of them do simmer if you're patient and willing to fiddle with them.  Here's a Reactor on low flame.

For a bit more on how to simmer, I'll refer you to this YouTube video that I put together.

Now, the question that is probably on every serious mountaineer's mind is, "how is it at melting snow?"  It's great.  It's super hot; it's wind proof; what more could you want?

Ah, but high tech though it is, it is still constrained by the laws of physics and therein the problem lies.  This is an upright canister stove.  On an upright canister stove, vaporized gas is fed to the burner where it is combusted, producing heat. In cold weather, gas doesn't vaporize very well.  There are a lot of factors that control whether or not a given upright canister type stove will work well in cold weather (you can see some of my other blog posts for more about this) and a Reactor will do better than some, but high tech or no, there's a point at which your fuel simply will no longer vaporize.  There are tricks you can employ like sleeping with the canister at night or carrying the canister inside your jacket by day and then using the first gas in the warm canister to heat up some water which is then placed in a spare pan into which you place the canister, but tricks like that can only take you so far.  My working number is 20F/-7C.  Below that, you begin to push your luck with an upright canister stove.  For all its technology, the Reactor cannot escape the constraints of physics.  Is it a good snow melter?  Sure.  Down to about 20F, maybe even a little lower.  But somewhere around that temperature 20F, you run into a hard stop, a hard stop that the Reactor's technology simply cannot overcome.

Note:  if you're a serious mountaineer and you're ascending to very high altitudes, you can operate a Reactor at lower temperatures than 20F.  Gas will vaporize at a lower temperature at higher altitudes.  But you'd better do your homework and understand just what the Reactor's temperature limitations will be for the altitude you'll be at.  Guess wrong and you've got no stove.  No stove = no water = dehydration which can lead to hypothermia which can lead to death.

Bottom line?  This is a great stove, but in cold weather you'd better darn well know it's limitations.

Thanks for joining me on another adventure in stoving,

HJ

The MSR Reactor

What's good about it
Hot
Wind proof
Stable
Hot
Well thought out
Extremely functional
Hot
Packable
Reasonably Efficient (if you don't run it on high)
Hot
Can nest an 8oz/230g gas canister inside the pot.
Liquid measures delineated on inside of pot
Did I mention hot?

What's bad about it
Expensive 
Heavy 
Bulky
Can eat a lot of fuel if you run it on high
Limited by it's upright canister type to temperatures of about 20F.
Can be tough to simmer.

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Stove of the Week: MSR WindPro

Stove of the Week: MSR WindPro

This week's stove is the MSR WindPro.


The WindPro is a remote canister stove, meaning that the stove uses a canister of gas that is attached to the stove via fuel hose rather than being directly attached to the stove.  Here you can see the stove and the gas canister as well as the fuel hose that connects them.


What's that you say?  You think the WindPro looks just like last week's stove, the Simmerlite?  Well you're right about that (Simmerlite, top; WindPro, bottom).


But take a look at the connectors.  That's what distinguishes the two.  The Simmerlite runs on white gasoline, a liquid fuel, and the WindPro runs on canister gas.


So, what's the big deal about it being a remote canister stove?  Well, on the more common upright type of canister stove, the burner mounts directly on the canister.  In other words, you have a very hot flame very close to a very flammable gas.  If you use a windscreen around the burner, you will deflect heat toward and trap heat around the canister.  Heat + flammable gas = bad.  Very bad.  Generally it's not a good idea to use a windscreen with an upright type canister stove unless a) you really know what you're doing and b) are extremely diligent about constantly monitoring the temperature of the tank via the "ouch" test (if the canister is hot enough to make you say "ouch," that's WAY too hot; TURN IT OFF IMMEDIATELY).  If you don't have a wind screen around your stove, on a windy day you could quite literally go through an entire tank of gas without ever bringing a pot of water to boil.  

Enter the remote canister stove.  If you put a windscreen around the burner, the canister, which is some distance away, will not be affected.  In fact, since the windscreen is between the canister and the flame, it's not only OK to use a windscreen, it's actually safer to operate the stove with a windscreen.  A windscreen not only makes your stove more efficient it also protects the canister.

Note in this photo how the windscreen sits between the canister and the burner, protecting the flame AND protecting the canister.


Add to that the fact that remote canister stoves have a much lower center of gravity and tend to be much more stable.  Particularly with a larger pot on top of a small canister stove, the arrangement can be quite "tippy," and your dinner may wind up spilled.

So, why doesn't everyone just use a remote canister stove?  I mean who wants to waste gas that they've just packed up a mountainside or risk spilling their dinner?  Well, first there's the up front cost.  Remote canister stoves can often be double the price of upright canister stoves.  Second, there's the weight.  An upright canister stove uses the canister itself for support; it has no legs.  Also, an upright canister has no hose.  The hose and legs of a remote canister stove all add weight.  Upright canister stoves are typically much lighter than remote canister stoves.  Then lastly there's compactness.  The legs and hose of a remote canister stove take up space.

In short, as in much of life, which stove is the better stove is a series of trade offs.  Which stove is the better stove for a given individual or a given use depends largely on the style of that individual, the conditions (wind, weather, elevation, etc.), and on the way in which the stove will be used.

For larger groups (and therefore for larger pots), the more stable remote canister stove is the better choice.
For areas prone to wind, a remote canister stove is the better choice.
For smaller groups or soloists, an upright canister stove will work just fine.
For those on a budget, the upright canister stove is the logical choice.
For fair weather, why not just take a lightweight upright canister stove?  Why carry more than you need?

But before you make your decision, there's yet another advantage to a remote canister stove, a big advantage: liquid feed mode.  First, let me be clear:  Not all remote canister stoves can operate in liquid feed mode.  In order to function properly and safely, a gas stove must have vaporized gas (not liquefied gas like the gas in the canister).  In liquid feed mode, to turn the liquefied gas in the canister into vaporized gas, a stove must have a generator (aka a "pre heat loop").  The generator is an area where liquefied gas is exposed to high heat such that the liquefied gas vaporizes (turns from a liquid into a gas).  If your remote canister stove does not have a generator, do not attempt to feed it liquefied gas.

How do I know if my stove has a generator?  Take a look at this photo.

Note the silver colored tube that proceeds from the left side of the burner around the front of the burner and up the right hand side of the burner.  This is the generator.   
Now, take at look at the top left side of the burner in the above photo.   If you look closely, you can see the generator, and you can see that the flames from the burner are actually hitting the generator.  Needless to say, the liquefied gas flowing through the generator is being exposed to high heat and does vaporize.

Well, that's very nice, but why should I care that I can use liquid feed mode?  Answer:  Cold weather.  Your stove needs vaporized gas.  In cold weather, gas doesn't vaporize properly.  In liquid feed mode you rely not on the weather but on the flame to vaporize your gas.  In other words, you can get the vaporized gas your stove needs even in weather that is quite cold.  Depending on the design of your stove, you may be able to operate your stove in liquid feed mode in temperatures down to -10F/-23C.  By contrast, an upright canister stove isn't much good in temperatures lower than 20F/-6C.  

Well, this liquid feed mode sounds very interesting, but as a practical matter, how do I go about it?  Well, you invert (turn upside down) the canister.  After inversion, the valve is at the bottom of the canister, and the pressure in the canister forces liquefied gas out the bottom of the canister.  Before you start, it's best to put something heavy (like a pot of water) on the stove so the stove won't tip over as you invert the canister.  The recommended way to use a stove in inverted canister mode is to start the stove in normal mode, let the stove get hot, turn down the flame to low, and then invert the canister, keeping the canister low the entire time.  The stove will surge a bit when you invert the canister because of the physics of a liquid turning rapidly to gas.  Keeping the canister low and turning the flame down low help keep the surge to a minimum.  Leaning the canister against something will keep the canister inverted (see photo).


Now, here's our WindPro, happily chugging away in inverted canister mode, and, as you can clearly see, she has handily passed the "tea test."


Ah!  I see that breakfast is served, so you'll have to excuse me.



I thank you for joining me on another adventure in stoving.

HJ

Some summary information:

What's good about it?
For a remote canister stove, it is light and compact.
It has a generator (pre heat loop) so it can be used in inverted canister liquid feed mode.
The fuel hose is long and flexible which facilitates using the stove in inverted canister liquid feed mode.
It's perfectly safe with a wind screen.
In liquid feed mode, it will work well in low temperatures, perhaps even subzero temperatures.  Note:  I'm not trying to be wishy-washy.  I just haven't done the field testing needed for me to feel confident in proclaming this a viable option in subzero weather.  
It's a canister stove.  Gas is really convenient.

What's bad about it?
The WindPro uses relatively heavy steel canisters.  Lighter canisters like the Powermax canister are available.
As with all canister stoves, you have the problem of what to do with empty canisters.  In some places there are some recycling programs, but recycling is not environmentally free.  There is some cost to the environment for delivering gas in convenient little canisters.
Inverted canister mode is a little "fiddly."  There are other gas stoves specifically designed for liquid feed mode that you don't have to fiddle with as much.
The pot supports are a little slidey.  They could be a little more grippy.

Overall, the MSR WindPro is a good light weight winter capable stove.

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Types of Gas Canisters

Article revised Nov 25 2011.

First, there are six main types of gas canisters out there, only four of which are really appropriate for use in backpacking.  The six are:
1.  The heavy steel, typically green, Coleman type 16.4 oz/465g 100% propane canisters.  These are great for car camping, but are generally too heavy and bulky for backpacking.
2.  The tall steel cylindrical canisters that look like a traditional can of hair spray.  These canisters contain, typically, 100% butane. These canisters are frequently used by the restaurant industry, particularly for tableside cooking.  These "long" butane cans have a "bayonet" connector that protrudes out of the canister's valve.  This "bayonet" is exposed and therefore vulnerable to accidental discharge or damage.  These to my mind have an inferior connector that is not robust enough for back country use although in some areas people do use them, particularly in Asia.  They are cheap, I will say that for them.

OK, so the first two really aren't for backpacking.  Let's get to the backpacking appropriate ones:
3.  The dome shaped canisters with a threaded connector.
4.  The dome shaped canisters with a smooth connector.
5.  The dome shaped canisters with a dimple in the top.

The dome shaped canisters with a threaded connector are the standard canister for backpacking in the US, UK, Australia, Canada, New Zealand, and Japan (and probably a few other places).  They're not unknown elsewhere, but they're not necessarily standard.

The dome shaped canisters with a smooth connector is the Camping Gaz type connector.  This is the standard in Europe.  Other types of canisters may be available, but they generally won't be as easy to find if you can find them at all.

The dome shaped, backpacking packing canisters with a dimple in the top are an older type of canister but are still the standard some areas including many parts of Eastern Europe, South America, the Middle East, and Africa.  These are piercable canisters.  The stove has a sharp piece of metal on it.  When you attach the canister to the stove, the sharp piece of metal forces itself through the top of the canister, puncturing a hole in the canister.  The canister is then locked into place.  Once the canister is attached to the stove, you cannot remove it until it is empty (unless you want flammable gas spewing everywhere).  This type of canister has been blamed for a number of accidents, and many countries have banned or have tried to ban them.  This type of canister is not recommended.  If the canister connection works loose, you could have a real disaster on your hands.  Avoid this type if you can, but be aware this is all that is available in some localities.

6.  Lastly, there is the Coleman Powermax canister.  This is a cylindrical, silver colored canister.  One end of the canister is rounded and has a non-threaded connector on it.  If you look closely at the connector, you'll see that the connector is hexagonal around the middle.  These canisters are actually a better canister than the standard dome shaped canisters, but they are not as widely available, particularly outside the US.  In addition, they require a specialized stove that has a matching connector.  These canisters will work in all conditions but are especially good in cold weather because they are liquid feed canisters.  Update November, 2011 on Powermax Canisters

See my earlier post on Winter Gas Choices for more on liquid feed gas stoves.

As I'm sure you've realized by now, not all canisters are available in all places, and in many areas no canisters of any type will be available.  If you plan to use your canister stove when you travel, do your homework.  Make sure the canisters you need are available in the area you are going to.

Generally all of the threaded dome shaped canisters are interchangeable.  Yes, I know that MSR says you should only use MSR canisters with MSR stoves and that JetBoil says you should only use JetBoil canisters with JetBoil stoves.  That's a bunch of bull.  They're interchangeable.  Maybe you'd have some problems if you bought some cheap brand in a remote country, but all of the ones sold here in the US have a standard 7/16ths UNEF thread and are interchangeable.  Where I live, Snow Peak is generally the cheapest and Coleman is generally the most expensive -- except at Walmart where Coleman gas is a real bargain at $4.88 for the 7.5oz canister. The brand you get for warm weather use doesn't make much difference.  I usually buy whatever is cheapest.

I've now broken out my discussion of which brands are best for cold weather into a separate post.  Please see What's the Best Brand of Gas for Cold Weather?  for further information.

HJ

Related articles and posts:

• What's the Best Gas for Cold Weather?
• How Cold Can I Run My Gas Stove?
• Gas Blends and Cold Weather Performance.  (Why not just use propane?)
  
• Stoves For Cold Weather I (Upright canister stoves) -- Seattle Backpacker's Magazine
• Stoves for Cold Weather II (Inverted canister stoves) -- Seattle Backpacker's Magazine

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How Gas Works and Winter Choices

Typical backpacking type gas canisters contain a blend of three gasses: butane, isobutane, and propane.

Each of these fuels vaporize at a different temperature: butane at 31F (-0.5C), isobutane at 11F (-11.7C), and propane at -44F (-42.1C). If your stove uses its fuel as a gas (i.e. a vapor), the fuel has to vaporize before it reaches the burner. If the outside temperature is lower than the vaporization point (boiling point) of your fuel, your fuel won't vaporize (it'll stay liquid), and your stove ceases to function. You can shake your canister and hear fuel sloshing around, but your stove is, quite literally, out of gas.

As the temperature declines and you pass each one of those vaporization points of the constituent fuels in your canister, you lose one of the components of your pressure.  Also, because propane has the lowest vaporization point, it has the highest partial pressure and burns off faster than the rest. In other words, in cold weather your best fuel gets used first, and only your lower performing fuels are left toward the end. As the fuel vaporizes as you use your stove, you get evaporative cooling inside the canister, and, the canister gets colder.  All these things contribute to "canister fade," increasingly weak performance as the canister approaches empty.

In cold weather (below 32F/0C), you've got a few choices:
1. Keep the canister warm, but you'll still have canister fade toward the end, and in really cold weather, keeping the canister warm is either difficult or dangerous (depending on the technique employed).
2. Switch to a liquid feed gas stove. You're still using the same three fuels (butane, isobutane, and propane), but they're fed in as a liquid, and the burner is doing the vaporization, so the outside temperature isn't as big of a deal.  See my posts on the Coleman Xtreme and MSR WindPro for examples of liquid feed gas stoves.
3. Go with liquid fuel (white gasoline or kerosene). 

Here are Hikin' Jim's general temperature range recommendations:
40+ F Regular Gas, Liquid Feed Gas, or Liquid Fuel will all work well.
30F - 40F Regular Gas, Liquid Feed Gas, or Liquid Fuel will all still work, but you're going to start to notice degraded performance on gas.
20F - 30F Regular Gas, Liquid Feed Gas, or Liquid Fuel will all still work, but you're going to notice degraded performance and you're going to have to use tricks on gas with many gas brands toward the low end of the temperature range.
10F - 20F You're getting below where regular gas stoves operate. If you're headed out in this kind of weather, do your self a favor and upgrade to a different type of stove. Yeah, if you fiddle with it enough, you can get your regular gas stove to work, but basic tricks don't work well down this low, and more advanced tricks can be dangerous. Dangerous as in severe injury or death. 
0F - 10F This is simply below the operational range of ordinary gas stoves. This is where liquid feed or liquid fueled stoves rule the day.
-10F - 0F No way in heck on regular gas stoves. Even liquid feed gas stoves can have trouble as you approach -10F. Specialized liquid feed gas stoves like the Coleman Xtreme will handle the cold better.
< -10F Liquid fueled stoves only.

OK, so there you have it. These are "rules of thumb" and are general guidelines only. No guidelines can cover all circumstances and conditions.

All of the above are ballpark numbers at best. So much depends on other things like wind, elevation, how you use the stove, what tricks you employ, how full is your canister, which brand of gas you're using, how sheltered a spot you're in, are you cooking in a tent or out in the open, etc.

HJ

Related articles and posts:

• What's the Best Gas for Cold Weather?
• How Cold Can I Run My Gas Stove?
• Gas Blends and Cold Weather Performance.  (Why not just use propane?)
  
• Stoves For Cold Weather I (Upright canister stoves) -- Seattle Backpacker's Magazine
• Stoves for Cold Weather II (Inverted canister stoves) -- Seattle Backpacker's Magazine

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Stove of the Week: Coleman Xtreme

Oh, my, look at the time.  Another week has passed.  It must therefore be time for another "Stove of the Week" (SOTW) post.   


Related posts:

• Stove of the Week:  Coleman Xpedition
• Stove of the Week:  Coleman Xtreme
• Update on Powermax Fuel 11/7/2011

Recently, a friend of mine who enjoys mountaineering asked the proverbial $64,000 question, "what's a good, light weight way to melt snow?"  A fair question I might add, and perhaps one that I can actually shed some light on.  So, for the next few weeks, my SOTW posts will focus on winter capable stoves.  In that vein, this week's stove is the Coleman Xtreme, shown here in full fury.


The Coleman Xtreme is a lightweight, winter capable liquid feed remote canister stove.  Coleman rates it as operational down to about -4F (-20C).  That's pretty dang good for a gassie.  I've read posts on the net indicating that it will operate down as low as -10F (-23C), which is extremely good for a gas stove.

Let's take her for a whirl, shall we?  For this week's post, we'll head over to the former Cobb Estate in Altadena, CA, now part of the Angeles National Forest.  Here we'll catch the Sam Merrill Trail to Echo Mountain.


At the top, we have a commanding view of the San Gabriel Valley.


For tonight's stoving, we'll set up here on what remains of the front steps of Echo Mountain House, a hotel built in the 1800's that burned down years ago.


The pot's on to boil!  


And in very short order, we've passed the tea test.


So, let's get to know a bit more about this week's stove.  For those whose eyes glaze over with details, I'll include a summary at the bottom indicating the pros and cons of this stove for winter use.

Here's a shot of the Xtreme deployed and ready to go.


--WARNING, POTENTIALLY BORING TECHNICAL SECTION--
Before I go too much further, let me define some terms.  First, there are generally two types of gas stoves:  upright canister and remote canister (yes, there are plenty of exceptions).  An upright canister stove is a stove where the burner mounts directly on top of the canister.  Examples would include the MSR Pocket Rocket, the Optimus Crux, and the original Jetboil.  A remote canister stove's burner is separate from the canister and draws gas via a fuel line.  Examples would include the MSR Wind Pro, the MSR Rapid Fire, and the Primus Eta Power.

Second, there are two ways to deliver gas to the burner of a gas stove, vapor feed and liquid feed.  In vapor feed mode, the fuel is delivered to the burner as a gas.  In liquid feed mode, the fuel, though it would be a gas at room temperature and pressure, is delivered still under pressure as a liquid.  You've heard the term LPG (Liquified Petroleum Gas)?  That's exactly what this is.  The gas is under such pressure that it liquifies into LPG and is delivered in that liquid state to the burner.

In terms of winter capability, why might it matter in what state the fuel is delivered to the burner?  Well, canister fuel typically consists of some mix of the following three fuels:  butane, isobutane, and propane.  Each of these fuels vaporizes at a different temperature:  butane at 31F (-0.5C), isobutane at 11F (-11.7C), and propane at -44F (-42.1C).  If you deliver the fuel as a gas, it has to vaporize before it reaches the burner.  If the outside temperature is lower than the vaporization point of your fuel, your fuel won't vaporize (it'll stay liquid), and your stove ceases to function.  You can shake your canister and hear fuel sloshing around, but your stove is, quite literally, out of gas.

If on the other hand, you deliver the fuel as a liquid, then obviously there's no need to vaporize the fuel as it leaves the tank.  Rather, the vaporization occurs at the burner where heat is available from the flame rather than from the surrounding air.  In order to heat the fuel to the point of vaporization, typically there is a "pre heat loop" (aka "generator") in the fuel line that extends into the flame.  Look at the very first photo in the first post of this thread.  Note the dark object in the flame.  This is the top of the loop.  The fuel flows out of the canister, down the fuel line, and into the loop.  The fuel is heated as it passes through the loop, and the liquid fuel turns to vapor, and the vapor exits via the burner and burns.

Hopefully I haven't lost anyone as I've explained this.  It is a little bit complicated.  If you didn't follow me completely, don't worry about it.  The bottom line is that a liquid feed gas stove can be used in temperatures that are much lower than those in which a vapor feed gas stove can be used.
--END OF POTENTIALLY BORING TECHNICAL SECTION--

Now then, one thing you should be aware of with this stove is that it uses a special Powermax canister as shown in the photo below.  


A Powermax canister has a hexagonal connector.


Note that this connector is completely different than the standard UNEF 7/16" threaded canisters (below).


The connector plugs into this assembly on the stove's valve:


It's important to know that this stove uses different canisters because these Powermax canisters are generally less widely available than standard threaded canisters.  In major metropolitan areas in the United States, it's generally not a problem.  For example here in Los Angeles, Sports Authority, Big 5, REI, and Sport Chalet all carry the Powermax canisters.  Elsewhere, such may not be the case.  However, because of the stove's nature, it has a loyal following.  One just has to make sure that the procurement of fuel is properly planned for.

These canisters do have several advantages:
1)  They are made out of light aluminum instead of heavy steel.  An empty 300g sized Powermax canister actually weighs less than an empty 100g sized standard threaded canister.  You're lugging around a lot less of the dead weight of packaging.  Packaging won't cook your supper.  Gas will.
2)  The canisters are side laying and are designed to feed fuel in liquid form with out the hassle of having to mess with fittings and having to prop up standard threaded canisters so that they'll stay inverted.  If that last bit about inverted standard threaded canisters didn't make sense, I'll come to that in another week's post.  Stay tuned.
3)  The canisters, when depleted, can be punctured and recycled just as you would an aluminum can.

Recall that I said that this is a remote canister stove.  Why might that be important?  Well, if your canister is directly attached to your burner and you use a windscreen, the windscreen will reflect heat back to the canister.  If your canister heats up to somewhere in the neighborhood of 200F (93C), KABOOM!, you no longer have a stove, you have an hand grenade, and let's just say that supper is now the least of your worries.

With a remote canister, the fuel is outside the windscreen.  Problem solved; you may use a windscreen without fear, and trust me if you're cooking in cold temperatures (remember, we are talking about melting snow here), you want every advantage you can get.  A windscreen not only blocks wind, but it traps heat, making your stove more efficient and keeping you hydrated.  Recall that staying hydrated is critical if one is to avoid hypothermia.

An Xtreme with a windscreen (perfectly safe):


Regrettably, though the Xtreme is a fine stove, it never achieved acceptance with the public, and Coleman has discontinued it.  Used Xtremes are still available.  Coleman is still selling at last check other appliances that use the Powermax canister, and Coleman has publicly committed to continuing to manufacture the Powermax canister.  Admittedly, this stove is a fairly specialized piece of equipment, and one has to go to a bit more trouble to procure and fuel it.  I submit to you, though, that this stove because of its unique and superior design is worth that extra bit of trouble and is therefore worthy of your consideration as a winter capable stove.

Let me leave you with one more shot of the Xtreme, here demonstrating her wonderful simmering ability.


This has been a most long winded post.  I thank you for your patience, and I thank you for joining me in another adventure in stoving.

It's now time to head back down the mountain,

and I therefore bid you good night.

HJ

SUMMARY OF PROS AND CONS
Pros
-A relatively lightweight, stable, wind-resistant (with a screen), winter capable gas stove.  The convenience of gas with good cold weather functionality.  That's the real hallmark of this stove.
-For a remote canister stove, the Xtreme is lightweight at about 11oz (312g).
-Can use a windscreen safely and easily.
-Rated to -4F (-20C) and quite possibly good down to temps of -10F (-23C).
-Lightweight, easy to use canisters.
-Simmers well
-Quite powerful.
-Fuel is generally less expensive than standard threaded canisters.
-Stable, can handle larger pots than upright canister stoves (you need to be able to handle a bigger pot for snow melting)

Cons
-Discontinued.  A used stove must be located*.  Parts will eventually become hard to find.
-Powermax fuel is less widely distributed.  This will be a problem in some areas and no trouble at all in others.

HJ

*Note:  The three legged Xtreme has a four legged sister, the Xpert.  Xperts for whatever reason seem to be easier to come by.  If you can't find an Xtreme, you may be able to find an Xpert.  Xperts typically are less expensive than the Xtreme, but they do weigh a couple of ounces more.

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