Go/No Go Thread Plug Gage Assemblies • Go/No Go taperlock Class X thread gage tolerance Tool steel constructionClass 2B plug gage assemblies are used to inspect internally threaded parts, and to verify min./max. pitch dia. limits. Class 2A set plug assemblies are used to verify and set adjustable threaded ring gages. SAE sizes meet ASME B1.2 standards. Metric sizes meet ASME B1.16M standards.