This illuminated bracelet is made of stretchy silicone with the LED light which is sound activated. Powered by two CR2016 round batteries and it can last up to about 40 hours, ensuring long hours of fun. There are 9 colors to choose from and one size fits most. Nicely visible while walking, riding, running, or on a motorcycle at night, and also suitable for club, disco, concerts, festivals, and other night activities. 8" C