Osprey Ultralight DrySack 6L Osprey’s Ultralight Drysack 6L is a simple yet effective way of organising and protecting clothes and equipment. The fabric is fully waterproof and has sealed seams so that no water can penetrate and the roll-top closure also acts as a barrier against the weather as well as allowing the volume of the bag to be effectively altered to better accommodate the contents. As the shape is rectangular rather than round, it is easier to pack more efficiently and the stuff sack can even stand up on its own.