With an R-value over 6, the 10cm thick EtherLightXT Extreme air mat redefines lightweight sleeping comfort for winter adventures around the globe. Sea to Summit's Air Sprung Cells are the reason you will sleep better on this air mat. Each Air Sprung Cell deforms independently and allows the mat to conform to your body shape. This provides support and comfort by more evenly dispersing pressure across the mat's surface. For the extra thick (XT) EtherLight design, many TPU loops are used to connect the top and bottom fabric layers to the Air Sprung Cell dot weld pattern. These loops allow the top and bottom layers to be positioned further apart which creates larger pockets of air when inflated-perfect for side sleepers. This design also requires less fabric overall which means great stability and comfort for less weight. Dual-density layers of THERMOLITE insulation fill the Air Sprung Cells and work together to prevent convective heat transfer and boost warmth while remaining lightweight and packable. When the mercury drops, the EtherLightXT Extreme's 6.2 (women's 6.3) ASTM R-value will keep you cushioned and insulated from the cold hard lumps and bumps beneath.