Thread pitches covered: .75, 1.0, 1.25, 1.5, 1.75, 2.0, 2.5, 3mm. 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.