Installed in the center of the wheel, won't affect the center of gravity of the bicycle. •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 on rainy days •Used to install children's bike wheel hubs for safe driving at night •Easy to install and remove. Automatically color changing Specification: •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 bikes) •Work Time: 8-12 hours •Item size: 82 * 82mm / 3.2 * 3.2in Package included: •1 x Bicycle Wheel Light •1 x Set of Rubber Gasket •1 x USB Charging Cable