the light is Set  on the bicycle valve ,it will be on when the wheel runs ,and flash
when you are driving at night ,it will bring more color to your bicycle .

WELCOME ,I LOVE YOU ,HAPPY TIME,GOOD LUCK" flash when cycle.

Fits on any  Bicycle,or the standard size air valve stem of any wheel
Motion activated, turns on automatically when you drive at night.
Turn off automatically when your wheels stop turning
Extra Batteries included and Batteries replaceable
Different light colors available: red, blue, yellow, green Compact design and light weight High intensity light increases visibility at night for safety
Makes impressive effects which vary with wheel speed -- all the way up to full motion circle
Water resistanceCopper material