This is an ultra-lightweight pack cover with excellent durability and water resistance. Its unique Just Fit System conforms perfectly to the shape of your pack, which changes depending on the amount of gear, minimizing flapping in strong winds. The design covers the entire upper back. In the event water does get in, the drain system at the bottom efficiently expels it. Material: Nylon Function: Waterproof Season: All Season Selling because I no longer need it after replacing my pack. In excellent condition.