【Limited Quantity Gift】 Starting today, receive one tail light as a gift with the purchase of this bicycle light! The tail light has 4 lighting modes and is waterproof. It will be shipped in simple packaging. 【Built-in Large Capacity Battery】 Side red light version. Built-in 18650 battery allows for long-lasting use. 【Light Sensor Auto-On】 Equipped with a light sensor that automatically adjusts the light on and off according to the surrounding brightness. Provides bright illumination at night and when riding through tunnels, enhancing safety. 【Easy to Attach/Detach & Anti-Theft】 Compatible handlebar diameter: Φ20-30mm. One-touch removal makes it easy to take off when leaving your bike. Can also be used as a flashlight when removed, making it convenient to carry. 【Wide Range of Uses】 In addition to bicycles, it is also useful for camping, hiking, night fishing, emergencies, power outages, and more. 【USB Rechargeable & Long-Lasting】 Fully charged in about 3 hours. Can be used for up to 72 hours on a single charge. With a battery level indicator for easy remaining power check. Usage time: Approximately 3-15 hours.