The Swiss Safe Emergency Mylar Thermal Blankets Premium 12-Micron 52" X 82" Silver 4-Pack is an advanced aluminized dual-sided thermal blankets are designed to retain up to 90% of body heat and are perfect for use in emergency survival situations, as well as home & industrial applications. Blankets are waterproof, windproof, and moisture-proof, helping to keep you dry in damp, wet, rainy, and downright cold environments. Perfect for hiking, outdoors, camping, backpacking, climbing. Can be used as ground cover, sleeping bag liner, or to prevent hypothermia and shock in extreme weather conditions.