This martingale collar is worked like a choke collar but without the chain. All-nylon collar will tighten when a dog pulls on a lead, then relaxes when the pulling stops. Also works to prevent dogs from backing out of their collars. Great for breeds with large necks and small heads like greyhounds. Includes a hangtag. Made of nylon and metal. Available in bluebird color. Measures 5/8-inch width fits 10-16-inch dogs neck.