They appear to be well made and reasonably priced but are surprisingly "tight". Bearings require a lot of force to turn. When installed in the system, I found that they slowed the rotation by almost 300 RPM compared to the old bearings they replaced. I thought maybe they just weren't lubed (?) from the factory and I got a good look at it through the mirrors. I have also sprayed lithium grease around the seals but found no beneficial effect. They may loosen up a bit over time, but so far they've been affecting my system's performance noticeably.