Union Butterfield 1500A(UNF) High-Speed Steel Hand Tap, Black Oxide Finish, Round Shank With Square End, Plug Chamfer, 5/16"-24 Thread Size Hand threading tap with straight flutes cuts threads in through holes and blind holes Black oxide finish improves lubricity, resists corrosion, and helps prevent buildup Available in UNC (Unified Coarse) or UNF (Unified Fine) right-hand thread options for different applications High-speed steel is compatible with a variety of materials Round shank with square end allows tap to be used in hand or power-driven applications