Model 6440 - Size 16, Stainless Steel, 3.0 mm Gauge 'Long' Links. Herm Sprenger collars are made in metric measurements, then converted to rounded-up inches for the U.S. market. Size 16 is 40 Centimeters long or approximately 15.75 inches long from ring to ring. For training purposes the collar length should be at least 3 to 4 inches longer than the dog's neck circumference to allow for training slack. Before use, wash metal collars in warm, mild soapy water to minimize fur discoloration.