Milwaukee's Thunderbolt Silver and Deming drill bits are designed for performance in low to high tensile strength materials, stainless steel and cast iron. Thunderbolt twist drill bits are made from premium industrial-grade steel with heavy-duty cutting surfaces that power through deep or shallow holes with lightning speed. A special flute geometry adds strength while providing increased chip ejection. Thunderbolt twist drill bits have a heavy duty 135 degree split point for easy penetration and a 1/2 in. reduced shank with 3 milled flats which prevent slippage in a jawed chuck. One per package.