1787515 Lenox 1-3/8" Nominal Diameter, High Speed Steel, Bi-Metal Selfeed BitExtreme durability high speed steel cutting edge for superior durability in nail-embedded wood stays sharper longerFast easy drilling, aggressive lead screw tip pulls the bit through material quickly and effortlesslyExtra lead screw and wrench included in every packageDeeper cuts, longer shank that cuts 4 Inch x 4 Inch without extensionQuick change impact hex shank allows for quick changing of the bits