Waterproof Bike Bicycle Rear Tail LED Helmet Cycling  FlashLight Safety Warning Lamp Cycling Safety Warning Light with Battery
Feature:
1.INCREASE YOUR SAFETY: The high-powered output will increase your visibility to the vehicles surround you in the dark. Visible 180 degrees, meaning the light is not only visible from the rear, but on both sides.
2.LIGHT EVERYTHING YOU OWN: Universal Mount. Fits any sized seat post or bike frame, 3 Strapping Sizes. Elastic Rubber stretchable to fit on almost anything! This light can be strapped on your helmet, backpack, bicycle seat post, back bike rack, stroller, and your pet's collar. Be creative and strap it on anywhere.
3.SAVE TIME & FRUSTRATION: No tools required. Conveniently strap-on in seconds on the go and remove in seconds when parked
4.RELIABILITY KEEPS YOU ON THE ROAD: Water & Shock Proof  - Runs on 2 X CR2032 Batteries & Features 3 Light modes: Solid, Fast-Strobe, Slow-Strobe
5.MULTI-FUNCTIONS FOR DIFFERENT APPLICATION: BIKE Headlight and Taillight Set-Headlight is with Headband which is perfect for BIKING /HIKING/RUNNING,Walking/BABY CAR
6.Multi-fit rubber strap-n-clip system allows for easy connection on and off handle bars 22-32mm, seat post or frame tubes 10-32mm

Specificaiton:
Powered by: 2 x CR2032 batteries (included,you don't need buy battery again
)
Diameter of lamp holder: 2cm 
Length of silicone belt: 9.8 cm 
Working Time: 50-160hours

Package:
1 * Bicycle Light