"MASTER,GAGE-NO 4 BEARING REAR AIR SEALING RING; USED TO INSURE THE DIMENSIONS OF THE PWA71652 AND PWA71655 GAGES AT 12.183 PORM 0.0002 AND 7.042 PORM 0.0002 RESPECTIVELY; CONSISTS OF STEEL BASE; 4 HARDENED REST PADS; 4 BLOCKS FITTED WITH REPLACEABLE HARDENED CARBIDE GAGING PADS; DIAL INDICATOR; STORAGE CASE"