COBALT STEEL Made from M35 cobalt steel, with molybdenum and cobalt added to create a hardened alloy, with a Rockwell hardness up to 67, extremely heat resistant; for much faster cutting and longer tool life, up to twelve times compared to an average HSS drill. NO CENTER PUNCH NEEDED 118 Quick-Cut tips are self-centering and penetrate quickly with less pressure. Will not \"walk\" or \"skate\". Straight shank provides a firm grip and precise centering, fits standard drill chucks and common round collet chucks. Must be used and operated at the correct RPM for maximum efficiency. 13 METRIC DRILLS The set includes 13 M35 cobalt steel twist drills: 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.2 mm, 3.5 mm, 4 mm, 4.5 mm, 4.8 mm, 5 mm, 5.5 mm, 6 mm, 6.5 mm. Well organized in a plastic case with an index for easy transport to your workplace. FOR METALWORKING Particularly effective for cutting hard metals such as stainless steel and cast iron, although they can also be used for softer materials. Not for hardened steel / high carbon steel. Try adjusting the RPM if it does not penetrate. Material: High-speed steel Category: Straight shank twist drill Cutting diameter mm: 1.5-6.5 Blade length (mm): 60 Total length (mm): 100