TRB RC10pcs 2x5x2.5mm MR52-ZZ Precision Ball Bearings Chrome Steel, Metal Shield

I was hesitant about these bearings because people were complaining about dimensional accuracy and leaving a bad review. I decided to go ahead and buy them anyway for my project and measure them with calipers. Let me begin by saying these are very tiny and very cheap bearings, holding perfect tolerances is not realistic. The actual dimensions are about 1.97mm ID (bore), 4.99mm OD, and 2.48mm thick (the product description should probably be updated to show this). For about a dollar per bearing, this is pretty great. The bore should be undersized like this so the bearing doesn't spin on the shaft, press fits are pretty standard for this type of thing. The shaft may need to be lightly sanded but that's fine for me. These work well and I'd buy them again if I need more in the future :)

A few rolled better than others, but overall still a great value for getting little bearings like this quickly,

It good product for every experimental study

Cosmetically, they look shining and like new, they are also clean, which is good.Functionally, they run fine and performance is just okThe big drawback is noise, very loud! Though I will keep them (as they are new indeed), but I won't recommend to other customers, as these bearings are far from satisfactory.

Bearings roll very smoothly.