Hands-on Gear Review
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Street Price: Varies from $61 - $90 | Compare prices at 3 resellers
Pros: Only 9 oz!, packs ultra small.
Cons: Uncomfortable for side sleepers, not warm, harder to deflate than other pads, air pump and pump valve add unnecessary weight..
Best Uses: Summer backpacking.
The Klymit Inertia X Frame is an innovative ultralight air core sleeping pad that uses baffles in key places to keep you off the ground and save weight. The pad is the lightest and most compressible “full length” pad we’ve tested. It weighs a mere 9.1 ounces and can fit in your back pocket when rolled up.
Although the Inertia X Frame is impressively lightweight and compact it has several drawbacks that restrict its use to a specific group of people. 1) The pad’s air baffles are “body mapped” to fit someone about 5’ 10” in height. Depending on how your body parts match up to it, the pad may not fit you. The pad is also the narrowest of the 17 we’ve tested – it’s 18” wide as opposed to the standard 20” width. Thus, wider people may not fit on it. 2) The pad is ideal for people who sleep on their back and don’t thrash about at night. You may not find the Inertia X Frame to be comfortable if you turn over frequently, sleep on your side, or curl excessively. Its varied surface makes it strictly for laying on and renders it incompatible with accessories that turn your pad into a camp chair. 3) The pad’s thin baffles and large open spaces do a poor job at insulating you from the ground below; the pad is best for summer use. 4) The Inertia X Frame comes with a hand pump that allows you to inflate the pad beyond what’s possible by mouth. Our testers found this to be unnecessary because an adequate pressure can be achieved by mouth. The pump and its additional valve also make the pad is close to two ounces heavier that it would otherwise be (see a more detailed discussion of this below). In sum, the Inertia X Frame could be a good choice for summer backpacking if you’re around 5’ 10” and sleep on your back.
Our top rated ultralight pad is the Therm-a-Rest NeoAir XLite, which weighs 12 ounces in the 72” x 20” size. The NeoAir XLite is more comfortable, warmer, and more versatile than the Inertia X Frame. We suggest the NeoAir XLite in size small (47” x 20”), which weighs only eight ounces (put your boots and backpack under your legs). Get the Therm-a-Rest NeoAir XTherm for ultralight winter activities.
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OutdoorGearLab Editors' Hands-on Review
The Klymit Inertia X Frame prioritizes weight and packed size over comfort. Weighing a mere 9.1 ounces and packing down to the size of a soda can, the Inertia X Frame is the lightest and most compact inflatable pad we’ve tested. Klymit uses body mapping technology to lift your butt, back, head and feet off the ground. The pad is shockingly comfortable if you’re sleeping on your back and reasonably comfortable when on your side.
Although the Inertia X Frame is ultralight, it’s definitely not ultra fragile. The pad has a 75-denier bottom and 35-denier top, which makes it plenty capable of handling normal abrasion. Klymit pressure tested the pad and says it can handle at least 10 psi.
Your body type will determine how comfortable the Inertia X Frame is. Our testers found the pad to be best for people around 5’ 10” plus or minus about three inches. Regardless of your, height, your body parts must correspond with the mapped parts of the pad. The Inertia X Frame is most comfortable for lying on your back. Side sleepers, those who move about at night, and those curl into a fetal position, will prefer a pad with a more uniform surface. People on the larger side and those with broad shoulders might not fit on the X Frame – it's 18” wide (10 percent thinner than the average pad in this class), and the single thin side rails make it feel even thinner than it is. The Inertia X Frame emphasizes weight savings, not comfort.
The pad’s one-inch thin and airy profile provides little insulation from the ground. It’s best for summer backpacking. Klymit suggests using the pad inside of a sleeping bag – partly so you don’t fall off of it and partly because the sleeping bag will help insulate your underside. Let’s discuss this further. A down sleeping bag may help fill some of the pad’s gaps, but we found this to be minimally effective because the gaps are primarily below the waist and midway up your back (places where you have the least contact with the ground). One inch of down loft helps a little bit, but not much, and a sleeping pad is only as good as its weakest part. Heat lost at the waist, feet, and head is not offset by the additional heat saved at the legs and at the small of the back. More importantly, most ultralight hikers use down quilts, which eliminate the zipper and bottom from a traditional sleeping bag. Furthermore, the best three-season and summer down sleeping bags have continuous horizontal baffles, which allow you to shift down from the bottom to the top of the bag (and vice-versa). When using a bag designed for summer use our testers generally shift as much down as possible to the top of the bag (to increase warmth). Thus, using the Inertia X Frame inside a traditional down bag is similar to putting a carbon fiber hood on an 18-wheeler: you’re reducing weight in one of the least efficient ways. Anyway, the Inertia X Frame is for summer use only.
The pad’s included air pump and pump attachment are curious features. These are designed to let you pump up the pad beyond what’s capable by breath. Inflating it super hard – Klymit claims the pad can handle over 10 psi – get’s you slightly farther off the ground and thereby keeps you ever so slightly warmer. One problem, though, is that the pad is less comfortable when it’s pumped up like a tire. From a performance perspective, the hand pump and its requisite valve are inefficient. The pump weighs one ounce and the valve, which is permanently attached to the pad, weighs close to an ounce, too. Inflating a pad with ambient air can be a wise move when camping on snow (water vapor from your breath condenses within the pad and can be hard to get out), but it’s unnecessary in the summer (when water vapor stays in gas form it comes out when you deflate the pad in the morning). Thus, we believe the pump and valve are unnecessary features that add weight.
On a less critical note, the Inertia X Frame is slightly harder to deflate than traditional sleeping pads.
If you carry the Inertia X Frame and its pump you’ll be carrying over ten ounces, which is only two ounces less than a Regular size Therm-a-Rest NeoAir XLite (72” x 20”). The NeoAir XLite is significantly warmer, more comfortable, and more versatile than the Inertia X Frame. What’s the ultimate ultralight pad setup? Put a small NeoAir XLite (47” x 20” and only 8 oz.) under your torso and your shoes and backpack under your legs and feet. This setup weighs eight ounces, and is warmer and more comfortable than the Intertia X Frame.
Ultralight summer backpacking for back sleepers around 5’ 10” in height.
If your body and sleep style fits the Inertia X Frame’s specific requirements $100 is a fine price to pay for an ultralight pad.
=Other Versions and Accessories==
Klymit’s Inertia X-Lite chops the bottom half of the pad off and saves three ounces and $10 from the X Frame’s retail price.
— Max Neale
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Most recent review: May 29, 2013
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