The Aquatherm is an insulated bag which completely surrounds a standard 32 oz. Nalgene bottle with 1/2" foam and a reflective insulation material. These sacks help prevent water from freezing while winter camping or mountaineering. They also work great for keeping hot drinks hot in the winter and cold drinks cold in the summer. Comes with a daisy chain and draw-cord opening with an inner insulated lid. The Aquasack is the ultra-light and less expensive version of the Aquatherm. Bottle not included.