To activate your fiber optic headband, flip the switch located at the top of the headband. LED colors will automatically change. NOTE: Due to packaging that will save you money on shipping, headbands require light 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 Base: Blue, Pink, Green, and Red Headbands with Fiber Optics include 3 replaceable AG13 Batteries.