Black Menba 4Pcs LM8LUU 8mm Longer Linear Motion Ball Bearings for Linear Motion on 3D Printer, CNC, and Other Applications

I bought two sets because I've heard stories about these things coming in with only half of them working, and I wanted to replace the 4 y-axis bearings in my Maker Select V2.1. I only had to open the first set as all of them slid pretty well. I did realize that one of the bars might be a bit off, so the bearings aren't sliding as well on that one in particular, but they are super smooth on the other.

I replaced the Y-axis bearings on my Monoprice Maker Select v2 with these. It's far quieter, and the replacement was simple.

All 4 bearings were bad. The linear rod would not even pass through without grinding. These are being returned.