Installed in the center of the wheel, won't affect the center of gravity of the bicycle Features: No speed is required, will constant lighting when power on. Separate design, easier to install, and suitable for mountain bikes and children's balance cars. Waterproof design, you can usually ride in rainy days. Used to install children's bike wheel hubs for safe driving at night. Easy to install and remove. Automatically color changing. Specifications: Diameter not exceeding 30mm is available Material: PC Battery Capacity: 300mAh Li-Battery (USB rechargeable) Installed Diameter: Less than 30mm (Especially recommend for kids balance bike) Work Time: 8-12 hours Item size: 82 * 82mm / 3.2 * 3.2in Package size: 86 * 86 * 37mm / 3.4 * 3.4 * 1.5in Package weight: 70g / 2.5ounce Note: No vibration is felt after 5 seconds of power on, and the light turns off intelligently. In the process of use, if the light do not feel vibration for 35-40 seconds, the light will go out automatically, and the light will turn on intelligently when it vibrates again. Packing List: 1 * Bicycle Wheel Light 1 * Set of Rubber Gasket 1 * USB Charging Cable