Manual & Automatic Mode * Manual Mode: Press and hold the center button to turn on the light in manual mode. In manual mode, the super bright brake light feature/function continues to work. * Automatic mode : Once the light is on, 2 short/quick presses of the central button switch to automatic mode and the central button lights up with a green square. After 30-100, the light turns off. Movement activates the light. Smart Brake SensorWhen the vehicle is rolling, bicycle tail light will automatically highlight (3 seconds) a red light to warn the vehicle behind to slow down. Especially at night, it can ensure your riding safety. Auto-sensing switch: The smart bicycle tail light will automatically turn on when riding in low light conditions, but it is not automatically turns off when no motion is detected within 30 seconds. When the bike is riding under strong light, bike light will automatically turn off. It can save your time to turn on the rear lights of the bicycle. Waterproof and USB ChargingBike light has passed IPX4 waterproof certification, built-in 350mAh polymer lithium battery and is equipped with a USB charging cable (charging method: computer, charger, mobile power or any other device with a USB port), fast charging After 2.2 hours, the bicycle taillight can be idle for 35 hours. < p>Durable Design, Easy to InstallCNC aluminum alloy shell makes the bike taillight so strong and portable (lightweight). A saddle mounting bracket and an adjustable silicone strap are provided to make the bicycle tail light flexible, which can be quickly installed and unscrewed from the bicycle and the seat post for loading. The smart bicycle rear light is suitable for any road bike. Note: Due to the light and screen setting difference, the item's color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement.