Caninus Collars 2" Width Martingale with buckle Dog Collar. Our collars are handcrafted with heavy duty nylon webbing, welded metal hardware. Each collar is made to order with your pup in mind. The Martingale Dog Collar was designed for Sighthounds (ie, Greyhounds, Whippets, Italian Greyhounds, Borzoi, Saluki, etc) because their necks are larger than their head and they can slip out of traditional side release dog collars; these collars have gained popularity as training dog collars with other breeds in the recent past because trainers prefer the humane choke aspects. Please measure your dogs neck before ordering a collar. If your dogs neck is in between to sizes please order the larger size. Our sizing is as follows: X-Small: 8"-12" Small: 12"-15" Medium: 14"-18" Large: 17"-24" X-Large: 20"-29" XX-Large: 28-34"