... for gaging API internal or external thread. Conform to: API 5B. CSG,LCSG,LP,BCSG,TBG,UPTBG,NC.. API Thread Gauges ... API internal and external threads.API Spec 5B:CSG 4-1/2 to 20"LCSG 4-1/2 to 20"LP 1/8 ... to 12"BCSG 4-1/2 to 6"TBG1. ... 050 to 4-1/2"UPTBG 1.050 to ... 4-1/2"All gages are produced in ...