The Lifesystems Thermal Bag is made from a durable metalized polyester laminate which works by reflecting and retaining 90% of your radiated body heat. In the event of an accident or trauma, or when the weather suddenly turns cold, the risk of losing body heat increases and can lead to hypothermia without the proper kit. This thermal bag provides total body coverage and the material is also waterproof and windproof. Simply open the bag, step in to it, and cover your head with the excess material to retain body heat. If needed the bright orange outer can also help other walkers or rescue teams locate your position.