Alfa Tools HTSPB71318 5/16-20 Hss Special Thread Tap with Bottoming Style Hand tap - special thread 5/16-inch-20 tap size, Bottoming style Bottoming taps (1 to 2 threads); used for threading close to the bottom of a blind hole General purpose taps can be used by hand or under power, in through (open both ends) or blind holes (closed one end) Quantity -1 per pack