Set includes 5 drill Bits from 1/4 to 1/2 sizes in the set include: 1/4", 5/16", 3/8", 7/16 inch and 1/2". Drill America cobalt drills are manufactured to National aerospace standard 907. These drill Bits display high red hardness, permitting speeds up to 30 percent greater than with conventional M2 high speed steel, and are especially effective in drilling tough, high tensile strength materials like stainless steel, Inconel, and titanium. The 135 split point is self-centering and reduces thrust.