The district rear light is bright now that may sound like an obvious statement but until you39ve seen one of these in the dark you won39t quite believe itkey features135 40105 measured41 lumens on maximum powerchoice of three static and three flashing modessupplied with a 2 cell es li ion battery or uses power from exsiting front light via splitter cableqr band seatpost mount 40aero post mount now available412 cell es battery uses an intergrated battery life indicator so no