How's Your Dog LED Flashing Nighttime Safety Pet Blinker -Blue & White Flashes Blue-White-Blue-White in a repeated sequence Visible up to 1,000 feet in the dark, perfect for nighttime walking or jogging Weatherproof, Shock Resistant and Virtually Weightless Powered by 3 replaceable AG3 Button Batteries (installed), up to 150 hours of battery life Measures approx. 1/2" W x 2-1/2" L