Keeping the body protected against the elements is vital to survival.These space age sleeping bags protect an individual much more than the basic space blankets. The bags are waterproof and windproof and retain 90% of your body heat. This is the same technology used by NASA to maintain the body heat of space explorers. It doesn’t have the openings on the bottom which is where most of the heat is lost in the emergency blankets. Don’t settle for anything less when stocking your emergency kits.