Good point Chuckbuster. I was thinking of a closer tolerance hole when I said about the minus being the 'GO' and the plus being the "NOGO'. For example, a hole of .250 with a tolerance of plus or minus .0002. The .250 minus could possibly be used for the 'GO' and the .250 plus could be used for the 'NOGO'. In cases like this, you definitly need to measure the plug gages to know the actual size as best that can be determined. If the .250 minus measured .2498 or .2499 and the .250 plus measured .2501 or .2502, then these would be acceptable 'GO', 'NOGO' gages. At times, I revert back to my days as a precision Jig Grinder. In the old days of manual precision grinding (pre CNC grinding), a good jig grinder could hold a hole size tolerance well within a total of .0001 of actual hole size, and a location tolerance within .00005 (not a typo).