The patented break-away buckle of the PetSafe KeepSafe Break-Away Collar is designed to prevent dogs from getting entangled by their collars. When pressure is applied and your dog begins to choke, it breaks away and falls off harmlessly. It helps prevent most accidents that happen when multiple dogs are playing at home, at the dog park or in doggie daycare when the collar gets stuck on a fence, deck, crate, kennel, vent, bush or tree. To keep your dog from escaping on a walk, just hook the leash clip around the two D-rings to prevent the buckle from releasing. To find the right size, measure your dogs neck and add 1. Made of nylon strap. Imported. Sizes:XS(0.38; 7-10 neck sizes), S(0.75; 10-14 neck sizes), M(0.75; 14-20 neck sizes), L(1; 19-28 neck sizes), XL(1; 22-34 neck sizes). Colors: Black, Blue, Orange, Purple, Red. Cancer and Reproductive Harm- www.P65Warnings.ca.gov. Type: Collars.