This is the top Brass Ring in the Cutting Head for the HTX, Hyper Gear, Mark III, and Optiplex. It is moved around by the set screws in the black aluminum ring (M517A0). The outside diameter is 56mm (2.205") and the thickness is 6mm (.236"). This part is used on the Cutting Head for the Hyper Gear, HTX, and the Mark III.
Mazak® Part # 46143300320