API thread Gauges usage: Used for checking API internal & external thread. Conform to: API 5B and 7. CSG,LCSG,LP,BCSG,TBG,UPTBG API Thread Gauges: Used for checking API internal and external threads. 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" Spec 7-2 NC10 to NC77 REG 2-3/8 to 8-5/8" FH 3-1/2 to 6-5/8" IF 2-3/8 to 5-1/2"
