Greenlee 00042 Screw Unit Assembly For Slug-Buster Self Centering Knockout Draw Stud, for 1/2-Inch Conduit Punches Self-centering punch aligns itself on pilot hole No need to draw crosshairs or line up die alignment marks Unique punch also splits slugs for easier slug removal Use with battery-powered, hydraulic, ratchet or manual drivers Draw studs must have matching Punch and die to operate