This review is for the Tres version, which is the middle size of the Especial bags. This one comes from Timbuk2, so you know a lot has gone into the features and design of the bag. It features a roll top layout that, when open, can greatly increase your storage capacity, but when closed offers weather resistance. It is not as waterproof as other bags, so if that is critical, you might consider other bags. A key feature of most Timbuk2 bags is the “Backbender” rear panel which is molded into the bag and allows for air flow. It also features routing lines for hydration reservoirs and headphones as well as a U-lock holster, making it a great messenger bag for you bike commute.