Manufactured from M35 cobalt steel, with molybdenum and cobalt added to creates a hardened alloy, measuring Rockwell hardness up to 67, for much faster cutting and extra longer life span, with up to twelve times when compared with an average HSS drill bit. No center punch is needed—the 135° Quick-Cut points are self-centering and penetrate quickly with less pressure. Will not "walk" or "wander" Extremely heat resistant; must be used and operated at 1500 RPM or greater for maximum efficiency. Straight shank allows for firmly holding and accurate centering, fit for standard drill chucks and regular round collet chucks The set includes 13pcs of M35 cobalt steel twist drill bits: 1.5mm, 2mm, 2.5mm, 3mm, 3.2mm, 3.5mm, 4mm, 4.5mm, 4.8mm, 5mm, 5.5mm, 6mm, 6.5mm Particularly successful in cutting through hard metals such as stainless steel and cast iron, although they can be used for softer materials, too.