5% COBALT TWIST DRILL BITS SET? Made from M35 Cobalt Steel with Molybdenum and Cobalt added to form a hardened alloy, can measure up to 67 Rockwell hardness, cut faster, last longer, and last longer than normal HSS drill bits 12 times. ? 115PCS SAE DIRLL BITS SET? The set includes 29pcs Fractional Size:1/16″ to 1/2″ in 1/64th increments; 26pcs Letter Size: A To Z; 60pcs Numbered Size: #1 To #60. Comes in metal indexed storage case for easy storage. ? TWIST DESIGN AND PERFORMANCE? Precise 135° SPLIT Point, Gold Oxide Surface and Round Straight Shank. Prevents walking and removes chips and particles faster. Precision fully ground to ensure smooth chip movement. ? PROFESSIONAL AND WIDELY USED? M35 Cobalt High Speed Steel is more suitable for hardening materials. Ideal for cutting stainless steel, steel and cast iron as well as wood, aluminum alloys and other metals. Not suitable for glass or ceramic materials. Pay attention to speed, pressure and heat control when drilling. ? SERVICE? If you have any problem with our metric drill bit set or are not satisfied with the product, please feel free to contact.