Feature: -Simple to use, long lasting, and safety attached -Easy mount and release , installed in seconds before you get ready to ride -LED strips easy heat dissipation and long service life -Suitable for 20 inch bicycle --Waterproof, but do not immerse in water for a long time Specification: Pattern is clear and completely when speed up to 20kms/hour. Equipped with light sensor and movement sensor, flash only at action, it will not work and save power when not riding. Material: PC Size: about 15cm x 3.8 x 1.5cm Color:as picture shown Battery: 3 x AAA battery ( not include), Could be maximed to 12 hours when it work. Note: Can flash 30 different patterns, built-in light sensor and vibration sensor, only work at night and in the dark. Anti-vibration, anti-fall, recommended speed is about 20 yards, two in one wheel is better If the riding environment is more complicated, it is best to reinforce the tail of the lamp to prevent the battery and LED lost.