LENOX® Tools Bi-Metal Self-Feed Bit Kit, 16 Piece (1787506), EXTREME DURABILITY, High speed steel cutting edge for superior durability in nail-embedded wood, LONGER LIFE, High speed steel screw tip increases wear resistance for extended life, FAST, EASY DRILLING, Unique parabolic screw tip pulls the bit through material quickly and effortlessly, RESHARPENABLE, Resharpenable with LENOX® Diamond File (product no. 25312DIAF1).