Big Agnes Zirkel UL 20 Degree Down Sleeping Bag Regular 850 fill DownTek water repellent down insulation - warm, dry and environmental friendl. Pertex rip-stop nylon - Featherweight, high thread-cout fabric that is soft as silk with a small packing volume. WR surface treatment to repel water Integrated half pad sleeve with unique design keeps you securely attached to the pad from the hips up while allowing freedom of movement for your legs, more like a traditional mummy bag. Never roll off you pad again! Half pad sleeve with adjustable strap holds ANY 20" wide rectangular or mummy shaped pad Mummy shape decreases weight & packed size. Recycled mesh 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 #5 zipper. Mate together any of Big Agnes' left and right zip bags with the same size zipper Flow Construction: Insotect Flow is a flow-optimized insulation system that delivers uniform heat distribution and natural body contouring through its revolutionary baffle design. Flow Construction eliminates lateral and vertical down shifting by using vertical chambers with Flow Gates to regulate fill positioning and density No-draft collar seals around neck to keep cold air from sneaking in. No-draft wedge insulates the connection betwen the bag and the pad. No-draft zipper tube insulates along the length of the zipper