Ether Light XR PRO is the warmest sleeping mat we make.  New and innovative Thermal Core® insulation allows the XR PRO to reach an R-value of 7.4 yet is small and light enough to carry in a rucksack. The Air Sprung Cells still provide four inches of stability and comfort regardless of sleeping position, while Thermal Core® insulation prevents convective heat loss and internal air movement. This results in outstanding comfort and warmth in very worst of cold weather conditions.Sea to Summit Ether Light XR Pro Insulated ASC Mat - Large Rectangular Features: 7.4 R-Value is perfect for cold weather adventures. At four inches thick, Ether Light XR Air Sprung Cells provides a plush sleeping experience regardless of your sleeping position. Duel layer Thermal Core® insulation fills the inner space, and includes a film that reflects infra-red radiation preventing heat loss due to convection and internal air movement. Lighter, quieter and durable 30D/40D face fabric with Sea to Summit’s liquid-extruded lamination is extremely reliable. Quick and easy inflation, deflation and adjustment is made possible by our XPRESS valve and supplied Airstream Pump/stuff sack. Anti-microbial treatment added to the TPU lamination formula prevents internal mold growth. PillowLock system prevents your Sea to Summit Aeros Pillow from slipping. Comes with a stuff sack which doubles as a pump, a repair kit with six self-adhesive patches and a spare valve insert.