The Seal Line Blocker Dry Sack. Featuring an efficient-packing patent-pending rectangular shape and strong fully welded seam construction Blocker waterproof dry sacks are the easiest way to organize and protect clothing and gear in your pack luggage or on a boat. Seal Line Blocker Dry Sack Features Space-saving: Patent-pending rectangular shape packs 20% more efficiently than rounded dry sack shapes saving space in your pack. Efficient-packing: PackTight™ packing system takes advantage of the flat-sided rectangular shapes of the Blocker dry sacks closely nestling them together for easy space-saving and intuitive organization. Waterproof strength: 50% stronger than sewn and taped seams all seams are welded to deliver superior strength durability and waterproof protection over time. Tough: High-strength 70-denier polyurethane-coated nylon is light enough to satisfy ounce-counters yet durable enough to stand up to life outside a pack. Eco-friendlier: PVC-free materials offer a reduced environmental impact over vinyl materials. Secure: Roll-top closure features a grippy stiffening strip to ensure a wrinkle-free secure seal when closing the dry sack. Easy organization: Available in 4 colors and 5 sizes making it easy to organize by both dry sack color and size.