The blackburn outpost top tube bag sits directly on top of your top tube is fairly large and will work wonders for the keen adventure cyclist the bag mounts securely to your frame via the top tube velcro straps and the head tube strap utilize the mesh and zippered pockets to stash an id or some cash and to keep a camera or other electronics device within reach open it up to find a large storage space with an adjustable organizer to hold hours of calories or other frequently used items made