Irwin Industrial Tools 1921ZR Taper Pipe Tap Set, 6-Piece Cuts internal threads in pipes. Ideal for pipe fittings. Nominal size of the tap is that of the pipe fitting being tapped Available in National Pipe Taper (NPT) and British Standard Pipe Taper (BSP) Tapered at a rate of 3/4-Inch per foot Includes one taper tap each of: 1/8" - 27 npt, 1/4" - 18 npt, 3/8" - 18 npt, 1/2" - 14 npt, 3/4" - 14 npt, and 1" - 11-1/2 npt. Made in the USA.