When it senses the brakes. It will enter highlight mode for 3 seconds. In intelligent mode. It will automatically turn off the light when you stand still for more than 1 minute. Automatically turns off lights in well-lit environments. Features: Accurate brake induction. Prevents triggering of brakes due to bumps. High strength aluminium alloy material. Automatically turn on/off depending on the light intensity and motion. Automatically switch to sleep mode to save power. IPx6 Waterproof. Easy to install, no tools required. 500m irradiation length, 220 degrees wide angle. Specifications: Fixed mode: straps fixed Item color: black Material: aluminium alloy, ABS, PC Waterproof: IPX6 Brightness: max. 60lm Battery: 3.7V, 350mAh Item size: 51 * 33mm / 2.0 * 1.3in Package size: 95 * 70 * 45mm / 3.7 * 2.8 * 1.8in Package weight: 75g / 2.6ounce Packing List: 1 * Bicycle Tail Light