TruThread R US
Thread ring gauge UNS

ASME B1.1
UNS threads (Unified National Special) are specialized threads that do not belong to the standard UNC (Unified National Coarse) or UNF (Unified National Fine) series. They are used in applications where a specific thread profile, pitch, or dimension is required beyond what is covered by standard UNC or UNF threads.

UNS threads are commonly found in industrial and mechanical engineering applications where precisely tailored thread characteristics are necessary. They can be either straight or tapered and are specifically designed for particular applications, such as aerospace, medical devices, and custom fastening systems.