Metric Thread Plug Gages - 6H, GO - NOGO These Metric Thread Gages allow you to inspect the pitch diameter and the functional thread for internal metric threaded products. All stock Metric Thread Plug Gages are made to standard tolerances per ISO1502 Standards. A Manufacturer Inspection Certificate is included with each gage. Each Thread Size includes a GO and a NO GO thread.Select Specific Thread Size from Pull Down Menu.