Chris Townsend tests out the latest sleeping mats best for the winter months. On test Therm-A-Rest NeoAir XTherm MAX Large sleeping mat

NeoAir XTherm sleeping mats are the warmest for the weight of any mats and also the lowest in packed bulk, making them ideal for cold weather backpacking. The latest MAX version is rectangular rather than tapered, which adds weight. The Large version sent for this test is also quite wide as well as very long – quite a bit longer than me in fact! This is not a mat for a small tent but if you’re heavily built and tall it would be ideal (and you probably don’t go for the smallest tents anyway). For me it’s too big. I’d much prefer the standard XTherm in the Medium size, which weighs 410 grams and costs £140. Indeed, if one of these had been supplied for test it would probably be Best Buy.

What makes the XTherm so warm for the weight?  There are two factors that make the mat warm without the need of any fill. The first is that the interior is divided into two layers of small triangular cells – over a hundred per mat – which keep the air in place and stop it circulating, reducing convective heat loss. The second is the presence of reflective layers inside the mat to reflect radiant heat back to your body. I suspect that the first of these is the real key to the warmth but whichever it is XTherm mats are very warm.

XTherm mats are very thick, which makes them very comfortable. The upper surface is textured so your sleeping bag doesn’t slide around on it.

XTherm mats are quite expensive and they do crackle a little in use like other NeoAir mats. This doesn’t disturb me but it might do a tent companion if you’re a restless sleeper. Unless you have one of the Therm-A-Rest pumps the XTherm has to be blown up by mouth. With the MAX L version this requires a lot of breath!