Versatile materials: Lightweight 70D polyurethane-coated nylon materials are a tougher, more resilient cousin to the ultralight BlockerLite materials. More durable and versatile, these materials are great for all-around use with confident waterproof protection. Smarter compression: Unlike conventional systems that pull against seams, our Continuous Compression system encircles the sack to minimize seam strain, maximizing durability for dependable protection. PurgeAir™-equipped: Our unique and waterproof PurgeAir valve vents trapped air, helping the sack compress further after being sealed, and is both more durable and more reliably waterproof than waterproof/breathable fabric membranes. Waterproof closure: Roll-top closure features a wrinkle-free stiffening strip to ensure a secure seal when closing the dry sack. Durable construction: Fully welded seams result in stronger and more durably protective construction compared to sewn-and-taped seams. Efficient-Packing: PackTight™ packing system sacks feature flat-sided, rectangular shapes that nestle closely together, packing 20% more efficiently than rounded sacks for easy, space-saving organization.