Smart Brake Sensor: When you brake, the sensor can sense the brake and increase the brightness of theVibration sensor Automatic turn On/Off: In smart mode, it will automatically turn off if there is no vibration for about 30 seconds, and it will automatically turn on when vibration is detectedUSB Chargee 260mAh Battery: Sufficient power for daily cyclingIPX6 Waterproof No worries in rainy days: Cycling as you want, regardless of the weather (Note:Dont put it in the water for a long time)Mini Size,Exquisite outlook: ABS plastic shell Lightweight material Only 23gPortable design, easy to install: Can be installed without toolsColour:blackMaterial:ABS+PCSize: 3.8 x 2.93cmPackage Contents:1 x Bicycle Taillight1 x USB data cableOnly the above package content, other products are not included.Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.