Polyethylene Versatile - The Go Time Gear Life Bivy Sack is a must-have in any survival bag. Each one functions as an emergency sleeping bag, a makeshift blanket, or as part of a survival shelter when camping. Ultra Durable - This reusable bivy bag isn???t just wind and waterproof. It???s also made from tear and puncture-resistant PET 26um mylar, with an interior that reflects 90% of your body heat. Escape The Elements - Need emergency shelter? Our survival bivy gives you cover in the rain, wind, and snow. Add extra warmth to your standard sleeping bag by using it as a liner in cold weather. Incredibly Compact - At 4.1oz, this lightweight thermal sleeping bag bivy won???t weigh you down. It packs down nicely in the 4??? x 3??? stuff sack and includes a 120-decibel whistle to alert rescuers up to 1 mile away. Go Time Gear Has Your Back - Whether you need emergency sleeping bags for survival, hiking, or for a bug out bag, our camping bivy sacks get the job done. If you???re not satisfied, let us know and we???ll make it right.