I'll admit I was a bit worried about the quality of these sockets as I was looking for an adapter for some of my 1/ 8" socketed. inch bits to my Makita trimmer (1/4" chuck). I had a chance to measure and test them today and all five from the package were machined to exactly the right dimensions. I have my router checked and everything worked as expected..Of course I'm not sure about their machinability at this point, but their dimensions are very accurate, the quality of the material won't be that important, and it doesn't seem that difficult or expensive to me, good ones to have enough quality for steel.in this application.there may be some production options but i can assure you mine received are excellent.recommended.