Sensitive Brake Sensing Light - With the sensitive motion detector, this red LED tail light will turn ultra bright when biker is decelerating. During riding, when the surrounding light is dark, the bicycle tail light will automatically light up.Convenient USB Rechargeable - Built-in 1400 mAh polymer lithium battery. Provides from 15 to 48 hours of running time. It can be fully charged in 2 to 3 hours. Comes with a USB port and a micro USB cable, you can get charged from any device like car charger, laptop/PC, wall charger and etc.Easy to Install - No complicated tools required for installation, easy to install and disassemble, fits in most road and mountain bikes. Equipped with a rubber band strap, you can install this bicycle taillight on the seatpost.IPX6 Waterproof Design - With IP66 waterproof design, this brake bike light is capable during raining or snowing or other bad weathers. The waterproof design broadens the usage scenarios of the taillights and prolongs the service life of the taillights.