Morse, SDHE11 (124508), Switchback, high speed steel step drills is for precision hole cutting in materials from plastics to metal. Designed to enlarge an existing hole, starting at 9/16", up to 1"diameter, in 1/16" increments (total of 8 steps). Sprial flute allows for faster penetration and cutting. Shank designed to work with 1/4", quick change, impact arbor adaptors. One (1) step drill per box.