Bontrager makes a really neat bag and rack combination. The Trek Interchange rack bag is designed so that it easily clicks to the Interchange rack. Once it is clicked to the rack it is very securely attached. It is not necessary to use velcro straps that might come undone and cause the bag to fall off. With the attached velcro straps the bag can be attched to non-Interchange racks, making it very versatile. The bag comes in three sized small, medium and large. Buy the basic small one, the deluxe one, the deluxe plus with fold down panniers, or the City Trunk bag.