Prevent your dog from giving you the slip. The PetSafe Martingale Quick-Snap Collar tightens when your dog pulls and loosens when they stop, ensuring it's tight only when it needs to be. More control means less risk of your dog slipping out and escaping. Quick-release snap buckle makes it easy to put on and take off. Safer than choke chains or prong collars, Martingale collars won't cause matting or bald spots like some standard collars. Custom fit is ideal for growing puppies, escape artists and breeds with necks larger than their heads. Durable nylon construction. Not recommended for tie-out use or during group play sessions. To select the right collar size, measure your dog around the top of the neck directly behind the ears. This measurement is the same as the collar when it's fully tightened or closed. Imported.