Smart Motion Sensor & High LEDThe built-in high-precision accelerometer, coupled with deep algorithms, swiftly detects various degrees of braking. When decelerating, the bike led light automatically illuminate brightly and remain lit for 2 seconds, conveying deceleration information to the rear. The ripple-shaped lampshade can refract light multiple times and offers six selectable lighting modes.Synchronous Mode: Stay synchronized with your team for better group travel. Double-tap to see the blue indicator light flashing, indicating the bicycle tail light has switched to synchronous mode. In synchronous mode, when two or more bike rear lights are in close proximity, all tail lights automatically synchronize their mode and blink at the same frequency. There are two installation options: saddle rail and seat post.Automatic On/Off: In intelligent mode, the system goes into a 2-minute sleep mode when idle. Lights automatically turn on upon sensing vibration, eliminating the need for frequent manual light switching. Comes with a 400mAH battery and a USB Type-C charging cable included. Remaining battery capacity can be observed by monitoring the side ring light.Light-sensitive Start-Stop: Smartly detecting ambient light, it automatically illuminates in low light and sleeps in bright light (without affecting brake light functionality). When entering tunnels or caves, there's no need to distract yourself by operating the smart bike tail light. With an IPX6 waterproof rating, the bike brake light can be easily used in any weather.Buttonless Design:Operating Instructions: To use for the first time, open the USB cover and toggle the power switch. Afterwards, use the touch-sensitive area at the center of the lampshade for power on/off. Mode Switching: 1. Long press the touch-sensitive switch at the center of the lampshade: Power on/off. 2. Single tap: Switch between 6 lighting modes. 3. Double tap: Switch between 3 modes - intelligent/manual/synchronous modes.