7 flash modes Get easily spotted by the others at night Compact design can be mounted to your seat post Specifications Size: 7.2cm*4.3cm*3cm Clip diameter: 1-5cm Suitable for seat tube diameter of around 3.5 cm Powered by: 2xAAA alkaline batteries( battery not included ) Specifications: 9 bright LED 7 flash modes Durable plastic High quality reflective cup Waterproof and shockproof Suitable for 3.5 cm seat tube diameter Package Included: 2x Tail light (battery no included) 1x Clip Notes: Due to different computer screen, the color of the actual items may slightly different from the listing images. Compare the detail sizes with yours, please allow 1-3cm error, due to manual measurement. Please leaving a message before you give the bad feedback, if the products have some problems. Thanks for your understanding.