The topeak redlite aero rear light is slim and aerodynamic and the simple tool fee rubber strap mounting system is quick and easy to set up on your seatpost or seatstay perfectly this topeak rear light has 2 modes to choose from either constant or blinking to ensure you get optimized visibility this light takes 1x aaa battery that is included and offers up to 80hrs of burn time finally the injection molded plastic lamp housing gives added durability topeak redlite aero rea