20 High Speed Twist Drill Bits & Organizer Great for Metalsmiths, Metal Working, Drilling & Organizing. This is a new set of 20 high speed steel twist drill bits. Great for drilling ferrous metals, tough casting sand forgings, working hardened stainless steel and other hard steels and tough high tensile strength nonferrous metals like titanium. These drill bits are ground and heat treated to a Rockwell hardness of 63. Sizes are stamped on organizer for easy selection and storage of proper drill size. These bits measure approximately 0.0135", 0.0145", 0.016", 0.018", 0.02", 0.021", 0.0225", 0.024", 0.025", 0.026", 0.028", 0.0292", 0.031", 0.032", 0.033", 0.035", 0.036", 0.037", 0.038" and 0.039" (0.34, 0.36, 0.4, 0.45, 0.5, 0.53, 0.57, 0.6, 0.63, 0.66, 0.71, 0.74, 0.78, 0.81, 0.83, 0.88, 0.91, 0.93, 0.96 and 0.99 mm).