Buckle 406 in Nickel, for 1/2 inch or 12 mm wide straps, collars, or belts.  Available in bright nickel (silver) only, these small center heel bar buckles are sized for straps or belts that are 1/2″ or 12 mm wide.  BKL-406: Pack of 10 for $8.00, or get 100 for $70, USA shipping included.