Thread pitches covered: 11, 12, 13, 14, 16, 18, 20 and 24 T.P.I. (threads per inch). These indispensable files restore damaged external threads on studs, bolts, screws, plumbing pipe and pipe fittings. Four different high carbon steel files are available. Each file provides 4 to 8 different thread pitches. Restores rusted or corroded fasteners. Doubles as a screw pitch gage.