NASA insulation material (polyethylene) Made in the USA STAY WARM IN ANY EMERGENCY: Designed for survival in extreme conditions, Sierra Madre’s thermal bivy sack reflects 90% of body heat, keeping you warmer for longer in cold weather. Ideal for survival kits, bug-out bags, camping, and hiking. WATERPROOF & WINDPROOF PROTECTION: Mylar was originally designed as a tear-resistant, insulating material by NASA for space exploration. Our durable PET emergency sleeping bag shields you from rain, wind, and snow, ensuring you stay dry and warm no matter the conditions. ULTRALIGHT WITH FULL COVERAGE: Weighing just 6 ounces, this survival bivy sack packs down small, fitting effortlessly into any backpack, glove compartment, or emergency kit for easy portability. Despite its light weight, our bag is larger for full coverage, fitting more body types comfortably. DURABLE & REUSABLE: Unlike flimsy emergency space blankets, our survival bag is tough enough for multiple uses. Just fold it up and store it back in the drawstring stuff sack for your next adventure. DURABLE & REUSABLE: Unlike flimsy emergency space blankets, our survival bag is tough enough for multiple uses. Just fold it up and store it back in the drawstring stuff sack for your next adventure.VERSATILE USE; A SURVIVAL ESSENTIAL: According to the Red Cross, the elements are the #1 killer in any crisis situation. Whether you're a backpacker, hiker, prepper, or a parent, the Sierra Madre Emergency Sleeping Bag is a must-have—because safety should never be an afterthought. ULTRALIGHT WITH FULL COVERAGE: Weighing just 6 ounces, this survival bivy sack packs down small, fitting effortlessly into any backpack, glove compartment, or emergency kit for easy portability. Despite its light weight, our bag is larger for full coverage, fitting more body types comfortably.