Herm Sprenger Black Stainless Steel Training Collar 3.2 mm Large Herm Sprenger Model 6425B | Prong Training Collar | Anodized Black Stainless Steel | (10) 3.2 mm Prong Links | Swivel D-Ring Center plate assembly from which five (5) prong links are linked on both sides of center plate with prong links placed directional toward martingale chain, placing even pressure on the neck sides and not on the trachea. Prong ends are beveled and polished. This model is placed around neck by pinching or squeezing a prong to open the collar Manufacturer factory assembled size fits neck size up to approximately 18 to 19 inches depending on fur type and fur depth. Manufacturer recommends this collar for dogs with maximum weight of 40 kg or approximately 88 pounds. Prong links can be added and removed to adjust fit. Additional prong links can be purchased separately. Read Product Description for additional instructions for sizing, fit, and care. Herm Sprenger authenticity is verified by the embossed logo on the center plate, specific rings, and junction components.