Sea to Summit Ether Light XT Extreme Insulated Air Mat

The Ether Light XT Extreme is Sea to Summit's cold-weather flagship air pad, built for four-season and winter use where insulation outweighs packed size. Its R-value of 6.2 (ASTM F3340-18 tested) sits near the top of the inflatable-pad category, achieved through Air Sprung Cell baffles filled with dual-density THERMOLITE insulation rather than reflective foil alone — a construction that resists cold-spot compression better than simple horizontal-tube designs. At 720 g in Regular size it is not an ultralight mat by summer standards, but the weight is proportionate to the warmth on offer, and it packs to a reasonably compact 24 x 18 cm. The 30D top and 40D bottom nylon fabrics favor durability over minimal weight, a repair kit is included for field fixes, and two valves paired with the included pump sack speed inflation while avoiding moisture buildup from lung-breath. Expect some crinkle noise from the Air Sprung Cell surface when shifting position. This pad suits winter backpackers, alpine base camps, and cold-sensitive sleepers who prioritize R-value over gram count.