8 diameters with a cordless drill for drilling a 1/4 stainless steel angle. I've never used one of these but decided to give it a try instead of a regular 5/8 drill. A regular 5/8 bit tends to crack when hand drilling, but this tool surprised me that the smaller diameters act like a pilot as it slowly but very effectively opens the hole to the full size I need. leaves a superior surface finish and good dimensional control. It's too early to tell how durable this tool is, but the edge still looks great and I'm very happy with the end result. Not bad for a vice and cordless drill.