As others say, it is helpful to have size described in millimeters. Fuji 5 horsepower compressor. I did not know either KIS - 6 or KMS - 28 A so purchase both. After all, milli standard KMS - 28A has been met.
I do not know whether it is millimeter or inches so I ordered both 20 mm and G 3/4 inch. In the actual measurement of a caliper, it was delicate whether the maximum thread diameter was 19.5 mm and 20 mm or 19.05 mm. The result was perfect for KMS - 20A. It is a cheap technique that you can do. If it is greedy it is easy to judge that actual size mm is included in combination with G 3/4.