These professional-grade cutters will totally drill-out spot welds, with little or no grinding required to finish the job. Make fast, clean cuts without cutting into the bottom skin. This solid one-piece cutter is machined from M2 tool steel. The self-centering point prevents "drill walking". Extremely durable and long-lasting - shop tested at over 300 cuts without resharpening. The 3/8" diameter cutter applies to most applications; the 1/2" diameter cutter is especially needed for trucks and convertibles. Drill at 700 - 2,000 RPM.