Herm Sprenger Dog Collar Herm Springer | Prong Training Collar | Stainless Steel | (10) 3.2 mm Prong Links Collar opens to 21 inch length | Initial size fits neck size up to approximately 16 inches depending on fur type and fur depth | Swivel D-Ring Meassure dog's neck and add 2 inches for initial collar length | Collar is opened to place around dog's neck by opening a prong link | Other models available with snaps Prong links can be added/removed to adjust length | Additional prong links can be purchased separately HS #6425S | Read Product Description for more information