The Big Agnes Lost Dog 0deg is a lightweight, synthetic fill bag, designed to excel in all conditions. These bags offer a roomy, rectangle-shaped sleeping space with an integrated Flex Pad Sleeve on the bottom. With technical fabrics and construction, 100% recycled, super-warm insulation, and tons of comfort features, this comfortable sleeping bag is designed to be lightweight enough for backpacking but cozy enough you'll want it in the campground too.