These ultra bright, bone-shaped LED lights are great for keeping your dog or cat safe at night. They are light sensitive, so they only activate in dim light and while your pet is moving. Each light has an ID label on the back and the LED is visible up to 1/2 mile. Each light is water resistant and features a metal latch to attach to collars. Measures 1 1/4" x 2" and works great for small to medium size dogs.