Rated to 0° Fahrenheit, the long-sized Eureka Wild Basin mummy-style sleeping bag features a bag-within-a-bag design, which keeps cold air from the outside from getting through and warm air on the inside of the bag from escaping. The inner layer of the bag is cut smaller than the outer layer to create a consistent thickness of insulation throughout the bag, which prevent thermal leaks from forming. The trapezoidal foot section is angled to allow for the foot's natural sleeping position. It has a fully adjustable contoured hood. Other features include a two-way, self-repairing zipper, inside stash pocket, fleece pillow pocket, and compression stuff sack.This sleeping bag is filled with Eureka's proprietary 7-hole slickened, polyester Thermashield fiber fill, which provides maximum insulation at the best value possible. Each Thermashield fiber strand contains 7 tunnel-like holes that run the length of the strand. Each of these holes traps air inside it's passageway creating dead air space that efficiently retains heat to keep you warm.