To activate your LED Shark Fin Headband, remove pull tab & press button on the side. Choose from many fun light functions: flash, slow change & steady lights. NOTE: Position headband ends in front of your ears for most comfortable fit – LED Fin will hug the back of your head. Dimensions (WxH): 5.5″ x 9″ LEDs: Multicolor Comes ready to use with 3 replaceable AG13 Batteries.