Herm Sprenger Stainless Steel Martingale Double Chain Collar, 18 inches x 2 millimeters, Black Herm Sprenger 50881-45-57 Size 18 is 17.72 inches | Two Row Martingale Collar | Anodized Black Stainless Steel | 2 mm link Double chain row for an attractive style-ish look beyond standard martingale Important: Herm Sprenger Collars are made in metric measurements. Size 16 measures approximately 40 centimeters or 15.75 inches. Measure dog's neck AND widest part of dog's head. Use the largest measurement to choose a size that will slip over dog's head and still allow slack for comfort and training communication Read Product Description for additional information about metric sizes, fit, use, and care instructions. Made in Germany.