Good quality bearing. The bearing turns well, but not very easily. This probably isn't a big problem because what's going to spin is likely to be heavy and has a lot of power. The bearing doesn't have much play and there are two set screws to tighten it up on a 15mm bar or whatever you run through the bearings. There are 2 mounting holes and they can be easily installed on almost anything. All 4 are individually wrapped and of the same quality. I am using them for a project and they are more than strong enough for my needs. I can't comment on how well they hold up to heavy use, but they seem strong enough for industrial use.