The Airstream Dry Sack is a lightweight and seam sealed nylon bag with
roll top closure and an Exchange Lite eVent fabric base. The base is
air permeable which allows air to be squeezed out of the sack as the
top is rolled down, thus creating a much smaller packed gear size.
Ideal for compressing and storing down jackets, belay jackets or
sleeping bags as it gives a 'vacuum packed' size yet remains
waterproof.