This IRWIN 5-Piece left Mechanics-Length Cobalt High-Speed Steel Drill Bit includes drill bits made of M-42 8 % cobalt high-velocity steel for A-one rough resistance in difficult metals. The 135 ° split point feed pressure for easier penetration without work hardening, and the heavy-duty spiral flute design produces swift chip ejection. The shorter drill bit length added strength and allows you to drill into fasteners without tightening them and often remove crushed fasteners without an extractor.