If processed well, these are good solid drills. I use them to drill 6061 aluminum and various types of plastic (ABS, PLA) in connection with my work building 3D printers and making plastic parts with these printers. The diameters are good, not crooked and not big. They cut well, although of course they cut aluminum better with a little oil. The coating will wear off over time after prolonged use or abuse. I'll admit I've made several oval holes with one racquet, but it didn't seem to have aβ¦