Originally developed for NASA. The Grabber All Weather Blanket pound for pound is warmer than wool. It retains 80% of radiated body heat, preventing hypothermia and providing unsurpassed protection in sub-zero temperatures. Made of layered polyethylene film, aluminum and Astrolar reinforcing fabric, this reinforced fabric blanket reflects 80% of radiated body heat back to you. Use for warmth under a tent, bivy sack or for emergencies. Compact size makes it ideal in a day pack for emergencies, or as part of an emergency kit in your car or home.