The flashlight tail cap is a way to lighten the end of your flashlight. The FTC operates in two modes: flash and constant on. It is perfect to use as a signal, to read a map, and to conserve energy in low light situations. Flash Tailcap 2 modes (Flash/Constant on) Watertight structure Driven Voltage: 3.0V-9.0V Fits all equal size flashlights of other brands driven at 3-9 volts For NEXTORCH model # T6A, T9, Z6, Z9