Nashbar RadFlash USB Tail Light. Not only is the Nashbar RadFlash USB Tail Light extremely bright 60 lumens on maximum setting, but it features a nifty design element to enhance visibility while saving power. Each of the RadFlash's five modes function only when the light detects motion. When stopped, the RadFlash automatically enters the Steady High Brake Light status until motion is again detected, returning it to the selected mode. Regarding the modes, there are High and Low options for both Steady and Flash modes, plus a Stopped Steady mode that doesn't emit any light while in motion, just the Steady High Brake Light when stopped. Powered by an internal, re chargeable via included USB cable battery, the light is compact, lightweight, and can be mounted or removed quickly from the seatpost via a tool free mount. Pair with the Nashbar RadBeam Headlight BN RDBM for a complete headlighttail light system.