By the way, your mail reads Ring Gauge 9/16-18UNF GRIR-2B and Plug Gauge 9/16-18UNF GPIP-2A, but each indication shall be corrected as GRIR-2A or GPIP-2B. If you want to describe each gauge precisely, you shall describe each size as 9/16-18UNF-2B GPIP or 9/16-18UNF-2A GRIR.