Country Brook Petz | Martingale Dog Collar - Plaid and Argyle Collection Collar fits 15 inch to 21 inch size neck. There are no standard sizes for dog collars. Please be sure to measure your dog's neck for correct size. Measure around your dog's neck (with string or tape measure) snugly where you want the collar to lay. If you have any questions or problems with sizes please give us a call before ordering. 256-974-0700 Breed Recommendation: Greyhound, French Bulldog, or Collie Made in U.S.A. with top quality hardware Traditional martingale collar has no buckle for superior strength.