Herm Sprenger Prong Collar Extra Links, 3.00 mm Herm Sprenger Model 6422 | Chrome Plated Steel Prong Link | 3 mm Package of 2 Prong Links. Dimensions are are 1.5 inches long x 1 inch wide (4 cm long x 2.5 cm wide). Read Product Description Section for additional instructions for size, fit, and care.