The Carradice Bagman racks with the quick-release allow you to easily remove the bag at the end of your ride and reinstall later. They attach to the saddle rails, and the QR portion is where you attach the bag. Carradice bags come in a wide range of sizes. Like I said, even the smallest one (Barley) holds as much gear as a typical racktop bag. The larger ones hold as much as small-medium panniers.