Instead, they unite the two. With Big Agnes, the pad slides into an integrated sleeve on the bottom of the bag, and the top two thirds of the bag is insulated in the traditional style. When insulation material is compressed under your body, it loses most of its ability to insulate. They eliminate the unnecessary bottom insulation and replace it with a sleeve to accommodate the pad which provides the insulation. Requires 2ea 20 in. wide rectangular pad sold separately. Integrated pad sleeve. Never roll off your pad again Double wide bag designed for two people Shell: Nylon rip stop. WR surface treatment to repel water Lining: Soft, breathable nylon with stain resistant finish. YKK 8 zipper. Mate together our left and right zip bags with same size zipper No draft collar 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 Features center no draft flap. Fabric piece with Velcro closures on the center gives you the option to attach the top of the body of the bag to the center of the hood to eliminate more drafts when you move in your sleep Synthetic insulation: SL90 synthetic insulation offers excellent warmth due to its approximately 20% higher loft than similar fills as well as a soft feel and great compressibility Built in pillow pocket holds a pillow Interior fabric loops for sleeping bag liners Cotton storage sack nylon stuff sack included Pad Sleeves: Nylon rip stop. WR surface treatment to repel water. Requires 2ea 20 in. wide rectangular pad sold separately Import.