The Irwin Tools 63129 29/64-Inch Cobalt 135-Degree-Jobber Length is made of M35 Cobalt Steel. The cobalt steel helps discipate heat, which is the killer of all drill bits, providing it with longer life and more durability. The cobalt construction allows this bit to drill abrasive materials like Stainless Steel and Cast Iron which are extremely tough on traditional high speed steel drill bits. The bit has a 135-degree split point tip to help eliminate walking as you start to drill the hole in metal. The straight shank works in both keyed and key-less chucks.