Alfie Pet by Petoga Couture - Kasey LED Flashing Pet Safety Collar with Photo Charm Keychain Set Helps incoming cars and traffic see both you and your pet in the dark. Also comes with one set (1 pc) of back-up battery for replacement. Collar is 0.75" in width and best fits pets with neck girth 12 - 16. Power button controls four modes of flashing: slow blinking, fast blinking, sustained lighting, and off. Sizing for each dog is unique. Similar to our clothing and accessory, medium size from one designer is not the same for another. For example our 9-pound yorkie model usually fits either one of three sizes (i.e. XS, S, M) depending on the designer. We highly recommend you measure your pet precisely with a flexible tape measure to ensure the best fit. Contact us if you have question. We are happy to help. Kasey LED collar, harness and leash are powered by individual LED bulbs, provide better visibility in greater distance. Its sturdy nylon fabric provide maximum durability and protection from rain and water. Keychain features sparkling bone-shaped photo frame, perfect for your favorite photo of wonderful memories with your pets. Conveniently detach hook to insert photo. Photo insert should be trimmed to 1.5 x 1.