"Topeak, Aero Wedge W/Straps Black-Medium Expanding compartments can boost your storage space in seconds. The Topeak Aero Wedge Pack is a convenient gear-toting solution that clips instantly to the back of your bike's saddle and seat post. Constructed of rugged 1,200-denier Cordura material with DuPont Teflon coating for weather resistance, the pack attaches with a Velcro strap mount and snap-on buckles. The expandable bag's large main opening offers room for all of your essential road gear, and a 3M reflective strip and rear light attachment offer safety-minded touches. Specifications 130-gram (0.29-pound) weight 60-to-80-cubic-inch capacity Measures 4.1-by-4.7-by-7.9 inches (W x H x D) "