How's Your Dog LED Flashing Nighttime Safety Pet Blinker for Large Breed Dogs-Blue & White Measures approx. 5/8" W x 2-3/4" L, equipped with Heavy-duty Xtra-Tuff? Lobster Clasp 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