If you're heading out on a trip and plan on bringing some extra gear back, or want another bag to keep you nimble once you reach your destination, the Ultralight Stuff Duffel is the answer. Packs down to nothing, expands to hold (most) anything; this duffel dissapears into your pack until you need it.
Stuffs into its own pocket
External zippered pocket with key clip
Main zippered compartment
Padded shoulder strap for comfortable carry