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 the others, but still at a low level of finish. The pens are ok but not very well sharpened or level. I'm sure they vary greatly from piece to piece. It's really nice that the 64's are available individually so I really appreciate that (wish they had 7/64's). be unusable (for the sake of accuracy) and a good straight 5/32" can be used instead as it's a nearer finished hole in comparison. I almost returned it for an exchange but it wasn't the time and effort worth.One of the other three has slight runout but the other two are ok.They cut decently - not as clean as good bits but acceptable..The sad surprise I noticed upon inspection was that it was on two bits along the grooves there was no relief - there is usually a bit of edge reduction behind the blades for friction and chip removal, but on the two largest the relief is almost zero Help and check what you get before you use them, they will burn/buff a hole (bad for glue) and are also a great way to loosen or break bits if the operator is inexperienced, finding them individually is not easy h, and they are not cheap. They will fit most of us and work for most applications. I wouldn't want this whole set, but filling in some of the empty holes helped.