Smart Speed Sensing: Once deceleration is detected, the taillight increases the brightness to high bright for 3 seconds, alerting vehicle behind. 6 Light Modes: slow flash, fast flash, strobe, breathing flicker, eco flash and steady on. USB Rechargeable: the rechargeable bike tail light built-in 350mAh Li-ion batterty, the taillight lasting 10-35 hours runing time in full charging of 2.5h. Made of aluminum alloy and ABS plastic, water resistant and shock resistant. Dual working modes: This Bike tail light can double-click to switch between manual /automatic . Specification: Type: Highly Brightness Bike Taillights Power Supply: USB & 350 mAH Li-on Battery Light Color: Red Charge: About 2.5 hours to fully charged, lasts for 10-35 hours Light Modes: Constant / Flash (6 totally) Size Chart: Size: approx. 31.3x28.3mm / 1.23x1.11 inch Package Includes: 1x Manual 1x Charging Cable 1x Bracket 1x Seat tube 1x Gasket 1x Bike Tail Light