10pc High Speed Twist Drill Bit Set #61 / 0.039" / 0.991mm / Drilling Bits 10pc High Speed Twist Drill Bits Great for Metal-smiths, Metal Working & Drilling The is a new set of 10 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 bits are sizes #61 - (0.039 in 0.991 mm)