I just got my order in from Mcmaster. I ordered 6 of these bearings and they are garbage. The outsides aren't milled smooth. The center part of the bearing wiggles back and forth like crazy. I also received 2 of the same bearings but in 3/8" and they are nice and tight and milled perfectly smooth. Another thing I would like to add is the way they pack those expensive precision rods. Just throw them in a tube with no packing. I had 3 rods in one tube with no packing and they got beat and banged around all the way to my house. They look like they will be alright. Just venting, sent email to Mcmaster about the bearings...