Intelligent Brake Tail LightBuilt-in high density speed sensor, when sensing the bike slowing down, the red light burst flash for 5 seconds. In Smart Mode, the brake lights fast flash for 5s, then the taillights go off automatically after another 8s. Tail light can work 17-35 hours in different modes.Vibration SensorWhen the bike is in a constant standstill for 20 seconds then it will start sleeping mode, and the bike rear light will wake up automatically when it senses the vibration.Mini Size: 1.97"x1.1"x1.45",55g.Waterproof & USB Fast Charging800mAh built-in battery, equipped with Type-C fast charging cable, you can connect it to plug, power bank, etc. for charging. Green light flashes when charging, green light is always on when full. IPX5 rated waterproof. Suitable for different weather.2*Mounting BracketsTwo different mounting methods, provide saddle mount and seat post mount, suitable for any road bike. Easy to install without tools. Net weight 55g, very light and easy to carry.