Extensively tested and reviewed by Cairngorm Treks throughout late summer and autumn 2018 in the Cairngorms and surrounding mountainous areas.

Coming in at a mere 258grams and packing down to around half the size of a regular lightweight mat, we were very keen to get our hands on the X Frame. This not a relatively new product and often gets talked about on various threads regarding ultralight trekking. Most will agree that the X frame appears to be truly innovative and quite an exciting prospect for a full length mat of this size and weight, but then back off a little when reaching to the pick this mat off the shelf, especially when considering a more traditional design compared to a product that without doubt has big holes in its design.

So let's start with the build of the Klymit X Frame. Before we open a product its always nice to see care surrounding packaging and appearance. This attention to detail often carries on through a product and let's the buyer know that a company has taken pride in their work. Klymit have hit the nail on the head in regards to this. Neatly packed into its small box we have a small stuff sac, the mat itself rolled up inside, a puncture repair kit, and a strange looking pump, similar in style to that which used to accompany our old camera kit for blowing dust off a lens.

The materials used for the mat are surprisingly tough considering its low weight. The X Frame has a 30d ripstop top paired with hardwearing 75d bottom. With such a small amount of material this tough fabric gives us confidence that is built to withstand extensive use. Like all air mats, punctures can occur and will need to be instantly fixed. The repair kit included is of good quality and is a great addition especially for anyone looking to use this mat for a long-distance expedition.

An area of interest is the valve used on the X Frame. It's twist and lock design makes for no air escape and the pump included means you can 'up' the pressure with micro adjustments. For us the modern approach of using a stuff sac as a pump seems to work better, but with just a few breaths to inflate we found we started to leave the pump at home as it just wasn't needed. With a large majority of air beds we tend to prefer a slight give in pressure to provide better comfort, but if you prefer a fuller mat then the pump included will be to your liking.

Where the X Frame really stands out is in the body mapping. Klymit explain that advanced patterning places chambers only where padding is needed and eliminates them where they are not, allowing Klymit to shed significant weight without sacrificing comfort. The best way to see if this design works is simply by trying it out. Klymit say you can place the X Frame beneath or inside your sleeping bag. We tried both choices over the course of a few nights and found it to be best placed inside the bag. At first we were a little unsure about having our bag touching the floor of our shelter but after a night of comfort and warmth we now understand the benefit of following this guideline. For a mat that has near zero thermal properties, other than simply keeping you directly off the ground, we found it instead added insulation by boosting the warmth usually lost from the bag itself. The fill of a down bag would usually be compressed between the user and the top of a sleeping mat. With the X frame, the body mapping design creates loft pockets in which our sleeping bag was free to expand and add warmth. This isn't to say it will replace a mat designed for use in the colder months and must be treated as more of a 2/3 season option. We generally paired the X frame with a 3-season bag rated at -1 degrees comfort. The combination kept us comfortably warm for use in the Cairngorms in which temperatures never really dropped below 0.

In terms of comfort the X Frame will divide opinion. For a mat that weighs in at only 258grams it's very impressive that once inflated it expands in length to 198cm. This suited our guides very well and although we do differ in height the body mapping meant we had sufficient padding raising us from the floor. This is all good if you intend to sleep on your back. For us side sleepers there are a few issues. Arms and legs would often come away from the padding and a few cold spots were noticeable throughout the night. If you sleep cold we would recommend you move towards a mat with full padding throughout. Warmer sleepers won't have much of an issue, although the occasional leg or arm might touch the ground the rest of the body would be supported throughout the night. In terms of comfort we would have to say that the XFrame is surprisingly very comfortable and much more pleasing to sleep on than its appearance might suggest. When looking to pack ultralight there has to be an element of luxury which is taken away, at this minuscule weight and pack size we were very impressed with what the X Frame gives in return and the odd leg or arm touching the ground wouldn't deter us from using the Kylmit on future expeditions.

Our Verdict

At the time of writing this review the Klymit Inertia X Frame is one of the lightest and most innovative air mats available. Designed specifically for ultralight expeditions it packs down to nothing and with just a few breaths opens up to a full-size mat of 198cm in length. Although minimalist in weight at only 258grams, it certainly isn't lacking in features, including a locking valve to make sure the XFrame stays inflated throughout the night, and a pump to make micro adjustments to the pressure to suit the user. We followed Klymit's advice for placing the XFrame inside of our sleeping bag and found this not only to keep the mat securely in place but also that it allowed the bag itself to add warmth from beneath through the innovative 'loft pockets'. The tough fabric used throughout has shown no signs of wear and we have full confidence that the XFame is built to last, something which can often be a worry when looking to pack super light for longer expeditions. Comfort is not to be expected to the same standard as a more traditional air mat, but we were happily surprised to find the XFrame to add much more comfort than its appearance might suggest. Although we used the XFrame for expeditions using single tents and bivvy bags, we expect this style of mat to work great on our upcoming woodland treks where using a hammock will be our preferred sleeping option. The price of the XFrame is also of great benefit, for anyone looking towards ultralight trekking this is a great piece of kit at a very good price compared to its competitors offering a similar weight.

Cairngorm Treks is a small family business based in the picturesque village of Tomintoul in the North East region of the Cairngorms National Park. They provide bespoke Mountain Guiding for Single Day Walks and Lightweight Multiday Trekking experiences, including wild camping, in the stunning Cairngorms wilderness and surrounding areas. Whether in the high mountains or lower valleys, their Multiday Treks are equipped with high quality, lightweight camping and trekking gear. They only work with small groups and, whatever your ability, pride themselves on designing your outdoor experience completely to your needs and with professional guidance and expertise. Adventure is waiting...