Trunk bag, aerodynamic shape, fully padded, expandable, integrated rain cover, for standard racks or for the ARKEL Randonneur Seat Post Rack. Most bags expand like a tower and end up collapsing sideways. We rather made the expansion sideways with a built-in expansion bellow for more carrying capacity when needed. Waterproof zippers keep the rain out, but for longer rides the TailRider has an integrated rain cover sewn into its own pocket. Just grab under the front flap and pull it out and over the Tail Rider. If what you carry needs a bigger, all encompassing volume, just remove the divider. It’s so simple! Leave it in the Tail Rider for the next time you need it. Not only does the Tail Rider feature a lot of reflective bands everywhere, there’s also a tab at the rear to hook a flashing LED light. Safety has no price. At the rear of the bag we located 2 D-Rings so you can clip a shoulder strap for easy carrying when off the bike. (Shoulder strap is optional and is not included with the TailRider) Technical Specifications - 660 g Weight (1.46 lbs) - 8-11 L Volume (488-700 cu inch) - Minimum Rack Width Required: 3.15'"or 80mm