2 Pack Polarshield Survival Emergency Sleeping Bag Silver Reflective Blanket (1034 2-PACK) 2 PackPolyester MaterialAluminum Coated OPP Material Designed From Insulation Used In Space Exploration Reflects 90% Of Body Heat To Help You Stay Warm Helps Prevent Heat Loss & Limits Solar ExposureEmergency Protection In All Weather ConditionsWeight: 5 oz LightweightReusableWater ResistantWindproof Compact For Easy Storage In Emergency Kits, Travel Gear, Car Or Home Great To Have Where Ever You GoDimensions: 84" x 36" A space blanket or sleeping bag (depending on the function, also known as a silver reflective blanket, space cover, Mylar blanket, emergency casualty blanket, first aid blanket, safety thermal blanket, hurricane weather blanket, heat sheet, shock blankets, foil blankets) is an especially low-weight, low-bulk blanket made of heat-reflective thin plastic sheeting. They are used on the exterior surfaces of spacecraft for thermal control, as well as by people. Their design reduces the heat loss in a person's body, which would otherwise occur due to thermal radiation, water evaporation, or convection. Their compact size before unfurling and light weight makes them ideal when space or weight are at a premium. They may be included in first aid kits and also in camping equipment. Lost campers and hikers have an additional possible benefit: the metallic surface appearance flashes in the sun, allowing use as an improvised distress beacon for searchers and also as a method of signalling over long distances to other people on the same route as the person who owns the blanket.