Description of Outdoor Research Advanced Hydroseal Stuff Sack #3 Features: OR stuff sacks have remained the benchmark in quality, design and function since their inception many years ago. The unique Hydroseal fabric that they developed combines a durable, 4 oz. Antron-nylon oxford cloth with OR's special Hydroseal-200® coating. Waterproof to 200 psi, and pliable at -40 degrees, The OR stuff sacks can take an amazing amount of abuse. Roll-down, dry bag-style top with Velcro® brand fasteners attachment. Slick and supple for jamming into kayak bulkheads and tight places.