Specifications: Installed in the center position of the wheel. It will not affect the center of gravity of the whole bicycle. The light suitable for cycle hub with a diameter of more than 35mm. Three kinds of flashing modes, quick, slew, steady flash controlled by a switch on side of light. Installation: Stick the rubber pad supplied on the inner ring. Encircle the light on hub, then tighten screws. Type: Bicycle Hub Light Material: Plastic Waterproof: Yes Modes: Flash, Wink, Steady Powered by: 3 LR44 Batteries(Batteries Include) Size: 9.5cm x 1.7cm/3.74" x 0.67" (Approx.) Install Aperture: 19mm - 36mm/0.75" - 1.42" (Approx.) Features: Waterproof, General, No Speed Requirements Notes: Due to the light and screen setting difference, the item's colour may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurements. Package Includes: 1 Set of Bicycle Hub Light