LED Light for Runners, Walkers, Cyclists plus Great for Concerts, Weddings, Parties, Pep Rallies and your Children will Love to Wear Them! (Yellow) Up to 50 hours of battery life on flashing modes - CR2032 battery Water Resistant Fits circumferences 10.25" to 11.75" Visibility up to 500 meters 4 Modes of Operation - Fast Flash, Slow Flash, Constant ON, and OFF