Fixed calipers:
Threaded plug gauge P/NP..
Made with non-deformable steel, with high wear resistance.
Material: 1.2842
Heat treatment: Hardening + tempering + CRYOGEN hardness: HRC.63+1
Surface treatment: BURNISHING
Thread Control: Metric (ISO)
Unified and American: Series UNC-UNF-UNEF Series 4-6-8-12-16-20-28-32 UN.
Cylindrical pipe thread ISO228/1.