Built-in 400mAh battery is rechargeable from any device with 5V USB output, such as computer, laptop, or power bank.. The rear turns off automatically in stationary state for 40 seconds, and turns on when any vibration is sensed. 5 modes switchable: Constant, Slow flash, Fast flash, Super fast flash, Breathing flash. Easy to use, hold the power button for 1.5 seconds to turn on or off. Front and rear set provides better visibility and safer riding at night
