This plug gauge is a standard tool for testing NPT threads.

Package included: AS your choosed

1* Taper Pipe Plug Thread Gage

The plug gauge has 3 step marks
Rotate this plug gauge into the inspected thread.
when Thread to “下” this thread Size Small Unqualified threads
when Thread to “基” this thread Size Standard Qualified threads
when Thread to “上” this thread Size Large Unqualified threads

Please refer to the attached picture:

Datacaciques