The NeoAir XTherm NXT has the best warmth-to-weight ratio ever achieved in a sleeping pad, with a weight of 440 grams and an R-value of 7.4. The underside made of 70D nylon is very durable.(The R-value measures a sleeping pad's thermal resistance, indicating its effectiveness at insulating against cold ground temperatures.– Summer-only backpacking/camping: R-value of 1 to 3– 3-season backpacking/camping: R-value of 3 to 5– Winter/4-season use: R-value of 5+)