The Drysacks are made of siliconized ripstop nylon, so your gear is protected no matter how wet your pack is. Osprey understands that your gear and organization requires a degree of flexibility, so udie Drysacks are available in sizes from 1.5L to 30L and in a variety of different colors. The Drysacks feature a waterproof roll-top closure, coated fabric, and sealed seams to ensure your gear stays dry in all situations. Unlike other drysacks, they are rectangular in shape. This makes packing your pack more efficient, and they can also stand on their own when they're not in your pack. What are you waiting for - protect and organize your gear!