The Mountain HardwearDryQBivy is a very useful product for all the hikers and campers. This bivy sac zips onto sleeping bags and keeps you dry when sleeping out in inclement weather. It is compatible with 70-inch zippers sleeping bags and has a drawcord closure system that clinches hood tight to hold in warmth. The sac has reversed DWR treated zippers that keep moisture out and comfort in. The taped seams of this bivy sac also offer complete watertight barrier making it a very reliable product. The fabric used to make this sac is waterproof and breathable, DryQ lite fabric which is known for its durability and performance. The zipper flaps are to make sure that there is no chance of water entering it. The Mountain HardwearDryQBivy also features a draw cord hood to cinch down when the storm cranks up.