Topeak Aero Style Seat Bag, Black Aero style seat bag with Integral Glow (Iglow) technology for safety at night Built in super bright .5W red LED within an optical fiber element which surrounds the bag Quick click mount F25 for fast, easy on/off and swapping between bikes Batteries included (2) CR2032 Dimensions 5.9"x2.2"x5.9" Weight 3.77 oz Capacity .8L