Easily tap tough materials by hand with this assortment of carbon steel screw thread insert (STI) plug taps from Hillman. Parts are designed to create threaded screw holes in various materials. This assortment features various plug taps which come in 13/64", 17/64", 21/64", 25/64", and 29/64" drill sizes. Full assortments of #59148 contain six (6) refills comprised of Hillman Item #'s 59149-59154.