Please Don;t take out the plastic panel and put battery into the case directly. Open the switch.It likes our ear,It will flash when it hear the music
One Size Fits All. Adjustable the velcro of the side to fit your face;
Volume Sensing Technology Automatically Calibrates From concert Volume to conversation Volume
Takes 2AAA Batteries (NOT INCLUDED)
Perfect for Riding,Skating at night and Many Sports, Halloween, Costume Parties, Masquerades, Mardi Gras, Rave Festivals, Carnivals, Gifts, and more;It is light and easy to ware.