Double thread restorers for internal and external threads, Inch Finish: Galvanised Whitworth Threads/inch, BSW thread, BSF thread24 3/16 and 7/32 --20 1/4 - 3/818 5/16 - 7/1616 3/8 - 1/2 and 9/1614 7/16 - 5/8 and 11/1612 1/2 and 9/16 - 3/411 5/8 and 11/16 - 7/810 3/4 and 13/16 - 1"