This isn't your father's (1970s) Bill's Bag. Now improved with the most nice shoulder straps in the industry and a clear vinyl strip for a better seal. 21-oz. PVC/polyester body and 34-oz. PVC/polyester round bottom. The 2.2 is small enough to fit in overhead compartments of most airlines, while the 3.8 offers plenty of storage for long excursions.