Master Rings Guaranteed acceptance or free - scroll down for details Lapped to size and polished. Non-gaging areas black oxidized - ring faces ground Meet all requirements of ANSI Specification B47.1-1988. Manufactured in accordance with ANSI Specification B89.1.6-1984. Master Discs AGD Style 3 Lapped to size and polished Meet all requirements of ANSI Specification B47.1-1988. Manufactured in accordance with ANSI Specification B89.1.5. Master Plugs Stabilized and hardened. 100 % usable gaging surface Ends ground square, lapped finish