Our martingale style collars are 2 inches wide and can extend from 21 inches to 29 inches (53.4cm-73.3cm) around. This collar can grow with your dog from puppy to adult and is not bound by belt loop holes, ensuring the most accurate fit every time. It has no buckles or adjustment rings on it; the adjustment comes from a heavy duty hook and loop system. The tightening action is completed with a large nylon loop, not chain, as to not pull your dog's hair or fur. This collar has a 5 inch (12.8cm) travel, so the smallest it can become after pulling is 18 inches (45.8cm). All D-rings and square-rings are made from stainless steel and the collar can hold up to a 400lbs load.