Taken from site...
"Stay at low camp or high camp in the REI Expedition -20°F sleeping bag featuring goose down insulation, a water-resistant/breathable shell and a double zipper system for temperature fluctuations."
Features* Unique double zipper system allows you to adjust comfort as needed—fully close both zippers to increase warmth, open inner zipper to decrease warmth
* Goose down is efficiently distributed for maximum warmth and compressibility—800-fill-power goose down on top and 700-fill-power goose down underneath
* Exclusive REI Down Fill Calculator optimizes the amount of down per baffle for the most warmth with the least amount of down
* Ultralight ripstop nylon shell fabric was specifically designed to dissipate moisture from the inside, as well as repel moisture from the outside, keeping
the down dry
* In-the-round pattern wraps vertical baffles around perimeter of sleeping bag, from head to foot, creating a 3-dimensional bag that wraps you in warmth
* Baffle spacing is optimized to keep down in place and prevent cold spots
* Multi-chambered hood and anatomically-contoured, insulated draft collar seal in heat; trapezoidal footbox mirrors sleeping position for room to move and thermal efficiency
* A pass-through pocket with zipper access on both outside and inside provides a convenient way to get to your stashed essentials such as eyewear and headlamp
* Includes nylon stuff sack and large cotton storage bag