I have bought four of these different sizes and they are fine. Just ok - not "very good" or "excellent" but ok. I have no way of verifying this, but it seems to me that this may be the lowest "industrial" high speed steel as M50. They're not very well made, of course, and three of the four bits have all sorts of holes and surface imperfections. I got it (after all, it doesn't matter, but it's a reference to reality and marketing). One of the bits is much better ground and finished than theβ¦