Smart Brake SensingWhen the bike rear light detects braking or deceleration, it automatically illuminates brightly for 2.5 seconds to increase visibility and warning effectiveness5 Lighting Modes: Press the button briefly to turn the bike light on or switch through the 5 brightness levels, and press and hold for 1 second to turn off. In the constant light mode, hold the button continuously to select between high, medium, and low brightness levelsAuto On/OffWhen ambient light is insufficient or vibration is detected, the taillight automatically activates. When there is ample ambient light, the taillight goes into automatic sleep mode to reduce power consumption250mAH Battery LifeThe rechargeable bike light comes with a USB Type-C charging cable, which can be charged using a 5V adapter, power bank, or similar methods. The charging time is approximately 2 hours, and the remaining battery level can be determined by the button indicator lightWaterproof:The highly sealed casing can resist sudden rainstorms. The led bike lights comes with a saddle clamp mount, as well as a seat post mount and strap, making it suitable for both round and shaped tubes