Features: The Battle Mountain uses two insulation materials to insure it's -15 degree temperature rating: 600 fill goose down on the top portion and bamboo synthetic on the bottom portion. This is the only bag in our line that has insulation on the bottom, between you and the pad. The New Battle Mountain features Bamboo Charcoal Synthetic Insulation on the bottom of the bag. This insulation is an eco-friendly, renewable synthetic insulation derived from bamboo which is burned at 800°C temperatures to create a charcoal that is then spun into a synthetic fiber. Integrated pad sleeve. Never roll off your pad again Rectangular shape offers more room in foot box and shoulders Cotton storage sack & nylon stuff sack included Built in pillow pocket holds a fleece or Big Agnes Pillow Interior fabric loops for sleeping bag liners 70" YKK #8 zipper. Mate together any of our left and right zip bags with a 70" zipper No-draft yoke seals around neck to keep cold air from sneaking in. No-draft wedge insulates the connection between the bag and pad. No-draft zipper tube insulates along the length of the zipper. Shell fabric: Down proof, nylon microfiber rip-stop. WR surface treatment to repel water. Interior lining: Soft and breathable, down proof nylon microfiber with stain resistant finish. Pad sleeve: Nylon rip-stop. WR surface treatment to repel water.