HEATSHEETS, from Advanced Flexible Materials, is a family of products especially well suited for First Responders. The blankets and ponchos feature a proprietary Silver Lining material and based on the radiant barrier technology developed by NASA for the U.S. Space Program. The silver lining, when worn against the body, reflects up to 90% of the user's body heat, giving great protection from Hypothermia. Or, turn the silver side outward and reflect the hot sun rays. And, HEATSHEETS are Waterproof & Windproof.