To activate your Fiber Optic Happy Birthday Headband, flip the switch located at the top of the headband. Words do not light up - they are covered in silver glitter. LEDs change color in the fiber optic boppers; 1 light function only. NOTE: Due to packaging that will help save you money on shipping, headbands require easy assembly. Fiber Optics arrive separate, so just plug them into the 2 spots provided on the headband. Dimensions: Height 7.50 in. Width 4.87 in. Fiber Optics Length 4.0 in. LED Colors: Rainbow Headband Colors: Assorted packs of Pink & Blue Headbands include 3 replaceable AG13 Batteries.