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Klymit X Frame Mat

Mini-review for the 2011 Lightweight Inflatable Sleeping Pads State of the Market Report


by Roger Caffin with Will Rietveld | 2011-08-23 00:00:00-06

Klymit X-Frame Mat - 1
Klymit X Frame Mat.


This mini-review is part of Part 2 of our survey of airmats. This Klymit X Frame mat is the most radical of all the mats tested: in some ways it looks like a space frame. Bits have been cut out to save weight and reduce the packed volume - but does it work?

X Frame

Klymit X-Frame Mat - 2

Length 180 cm / 70.9 in
Width 39 cm / 15.4 in
Thickness 3.0 cm / 1.2 in
Shape Roughly rectangular
Weight 236 g / 8.3 oz
R-Value See text
Drag Force Not measured
Insulation None
Inflation Blow or external air pump
Larger Side Tubes No
Material "Ripstop 30d top and coated 75d bottom"
Repair Kit No
Stuff Sack No
Price US$100

Klymit X-Frame Mat - 3

This was judged the most radical mat in the whole survey. It comes from a company which started out with the intention of using compressed argon gas to inflate jackets as a substitute for filling them with down or synthetic insulation. They were hoping to inflate the airmat the same way, but it seems they were persuaded that walkers would not be carrying around cylinders of compressed gas. So they now provide a very small but rather heavy 37-gram (1-oz) plastic pump instead. We describe the pump as 'heavy' relative to the amount of air it pumps per stroke. Mind you, it does not take a lot of air to inflate this pad: only a few very big mouth-puffs is adequate. However, it takes a lot of pumping with the little pump.

The first thing you notice when you come across the X Frame mat is that it has great big holes in it - great big cut-outs. Klymit claims the cut-outs have been "designed with body mapping technology; it gives you support and comfort where you need it and not where you don’t." However, that assumes that your body is the same height as that of the designer. If not, then I am afraid some of the gaps may be in the wrong places for your body.

Inspection of the mat shows some very nice engineering work. The top and bottom fabrics are nice. The top fabric is light and rather slippery, while the bottom fabric is heavy and feels much rougher. There is an outlet valve which looks very conventional, and you could blow the mat up with your mouth using this valve, But there is also a neat inlet valve which mates with the little pump they supply: it looks very much like the sort of socket you find on water bladders and filters. A bit of instruction is needed here: you must press the side clip in (as for a bladder connection) and then push the pump connector right in before letting go. If you don't, the stop valve inside is not opened and you simply cannot pump the mat up this way. (I wonder how I know that?)

The fabric is joined together using some sort of welding (I think). The method used is very tidy and professional. It would be interesting to see a 'conventional' mat made using this fabric and welding technology. The cut-outs on the unit supplied seem to have been done with a pair of hand-held scissors: the edges were a bit ragged. That does not matter of course, but it looked a bit strange. We understand that this was one of the hand-made pre-production units, and that the production units are cut out properly with a die. Also slightly strange: Will's mat had the inflation valve on the left side and the deflation valve on the right; my mat had the valve positions reversed. Not important, but a bit odd. Probably again due to them being pre-production units. (I do wish they would tell us these things when they ship pre-production units for review!)


Measuring the R-value of the X Frame mat was difficult, but for somewhat different reasons than you might have expected. First let's explain what the three bars in the graph mean. The first bar, labeled 35 mm, gives the R-value (2.0) measured at the hip region with the pad reasonably fully inflated and about 35 mm thick. The instructions from Klymit do say you should inflate it fairly hard: that's probably because there's not much of it supporting you. But of course, a fully inflated mat is a bit harder than a partially-inflated mat for sleeping. On the other hand, it is unlikely that the mat would be 35 mm thick under your hips or shoulders when you are sleeping on it.

The second bar, labeled 35 +, is for the mat under the same conditions but with extra insulation around the heater box and spreading outwards from it. This is meant to emulate the effect of having your quilt or sleeping bag spread out over the mat. The value is 2.1 - just a whisker higher and of questionable statistical significance.

Where the fun starts is with the third bar, labeled 'Hole'. This R-value was taken over one of the holes in the mat, and it is 2.8. That is, we positioned the heater box over a hole rather than over a conventional bit of the mat. The R-value is higher - why? The answer is complex and highlights some problems with the concept. When measuring a conventional region it is possible for warm air to circulate from under the heater box outwards along a tube in the mat, to cool off elsewhere. This happens with a mat in real life of course: warm air from directly under you can circulate out to a corner of the mat which is not covered by your quilt or bag. The way the sides or ends of the mat stick up in the air sometimes would increase the tendency of the air to circulate. But the air in the cut-out region or hole cannot circulate like this: it is trapped. Consequently the apparent R-value is higher. Incidentally, the company is well-aware of this phenomenon.

Is this increase in R-value significant or reliable? Well, that really depends. Let's imagine that you are using a quilt and lying on the mat over a hole. How will your body perceive the effect of the hole? To answer this you will have to decide whether you have a flat bit of your back over the hole or something like a hip or a shoulder. For a flat back, which is like the heater box, you might be fine, but if the bit of you over the hole is 'lumpy' it just might stick down through the hole far enough that it is very close to the cold ground - or touching it. In that case we suspect that you might find it a wee bit cold and uncomfortable.

This highlights two things. The first is that the pad dimensions are really designed for a person of one height and shape, with little flexibility for those of us who are either much shorter or much taller. The second thing is that the X Frame mat is really not suited for use with a quilt. It has been designed for use with a full sleeping bag. Indeed, Klymit does state that:

The cut out regions of the pad not only reduce the pad's bulk and weight, but is the basis for Klymit's patent pending loft pocket technology. Loft pockets allow the insulation on the bottom of sleeping bags to maintain loft and warmth beneath your body, where it would normally be compacted and useless, while promoting breathability.

Imagine that you are lying on it while inside a sleeping bag. The bit of your bag over the hole will not be squashed flat by your weight: it will stay a bit lofted. Great insulation there! Alternately, since the X Frame is so very narrow, you could put it inside your sleeping bag (maybe, size permitting). Once again, there would be some down filling the hole.

Mind you, in either case some of your sleeping bag is going to be touching the groundsheet. A pity if there is any condensation falling onto the groundsheet from the roof and rolling under you, or if a faint amount of water seeps up through your not-quite-100%-waterproof groundsheet (like some silnylon groundsheets these days.) That is not so clever.


We did try to measure the drag force, but the holes in the mat just did not want to cooperate. It does not seem slippery.

Comments by Will Rietveld

I used the X Frame pad on three backpacking trips, one with my wife where we both used it. The X Frame is obviously "different," and the question is whether the advantages outweigh the disadvantages. On the plus side, it is a full-length pad that weighs just 8.6 ounces (my measurement), it inflates very easy (four deep breaths), and did not slide in the tents I used. The pad is sized well for me (6' tall).

On the minus side, I found it hard to keep my hip and shoulder on the intended areas of the pad. When turning over at night, it was easy to move onto open areas of the pad. Also the pad is narrow, and it's harder to stay on it. The pad is fairly thin and I found it to be just barely comfortable enough. It helps to inflate it as hard as possible by mouth.

We were testing a prototype tent made of a waterproof-breathable fabric on one trip. The tent leaked and we had water on the tent floor. The X-Frame's "comfort chambers" made matters worse because our sleeping bag extended down through the openings in the pad and contacted the water, getting the bag wet.

Although I like the light weight and fast inflation, the X-Frame is not a favorite pad because of its lack of comfort. I would rather use a lightweight pad made of lighter materials (like the TAR NeoAir or Kooka Bay) that provides sufficient surface area (no holes) and more comfort.

Comments by Roger Caffin

Klymit X-Frame Mat - 4

Will is taller than me. He says he had some trouble keeping his hips and shoulders on the right bits of the mat; I'm about 170 cm (5' 7") tall and I simply could not support both my hips and shoulders at the same time. In addition, I found that my hips ended up on the ground even when I had inflated the mat fairly hard. There is just not enough mat surface underneath me to prevent that, possibly due to my shorter height.

The mat is rather narrow to start with, at just 39 cm (15.4 in) compared to the typical 50 cm (19.7 in) (and that is being slightly generous). But when it is inflated the tubes can sort of scrunch up as well, as shown here. Fortunately lying on the mat generally flattens it out, and the bigger hip region is not as susceptible to this problem. Does it matter? Probably not. The narrow width does let you slide it inside a large sleeping bag, something you could not do with a full-width mat. However, that would leave your sleeping bag in contact with the groundsheet, and any condensation which falls to the floor is going to end up inside your sleeping bag.

Did I take it out and field test it? Well, caution indicated that I should try sleeping on it at home first, and I found it was just not comfortable enough. I think the problem was that my body height just did not match the spacing of the mat sections. So I am afraid it never made it past the starting gate - for me at least. But I would be very interested in seeing a 'conventional' mat made with the same engineering.

This is a mini-review in the 2011 Lightweight Airmats State of the Market Report. The articles in this series are as follows (mini-reviews can be found in Part 2), and a subscription to our site is needed to read them.

  • Part 1 covers the basics, testing methods, and lists all the mats in the survey.
  • Part 2 examines the actual mats, and the performance of each mat tested.

Disclosure: The manufacturers provided these products to the author and/or Backpacking Light at no charge, and they are owned by the author/BPL. The author/Backpacking Light has no obligation to review these products under the terms of this agreement.


"Klymit X Frame Mat," by Roger Caffin with Will Rietveld. (ISSN 1537-0364)., 2011-08-23 00:00:00-06.