AMPRO T75623 Rethreading Set UNF and UNC, 18-Piece Repairs or renews damaged threads on nuts, bolts or studs, pieces are highly tempered, and hex shaped to be used with a socket or wrench 16 rethreading dies and 2 thread files in the set Die are National Coarse Silver 1/4, 5/16, 3/ , 7/1 , 1/2, 9/16 ,5/8 ,3/4-Inch, and National Fine Black 1/4, 5/16, 3/8, 7/16, 1/2, 9/16, 5/8, 3/4-Inch Thread Files for repairing threads, 8 sizes threads per-Inch are 10, 12, 14, 16, 18, 24, 27, and 32