For internal threads. 7-pc UNF (fine threads). Incl. 1/4"-28, 5/16"-24, 3/8"-24, 7/16"-20, 1/2"-20, 9/16"-18, 5/8"-18. Used to restore damaged internal threads. This are special threaded restoring taps that ensure a good result and they are safer in restoring threads than using regular thread cutting taps and dies. Regular cutters are sharper and can easily further damage existing threads. Packed in a re-usable clamshell package. USA made.

Note: Not suitable for cutting new threads.