I gave the wheels on my Harbor Freight trailer a spin the other day and one of them felt a bit rough. Upon disassembly, I found the inner bearing had been smoked. So it was off to the local parts store for a regular old 1 inch spindle bearing kit.
Oops. This trailer doesn't have a 1 inch spindle. It has a 25mm spindle. And instead of a 1.98" OD cup, it has a 52mm OD cup (2.05"). That's a big enough difference to not work. The regular old seal doesn't fit either.
I have purchased new bearings from a local bearing supplier and I have purchased extras in case of a break down in the future.
Most of my info comes from here:
Folding Utility Trailers, Trailer Kits, Parts and Accessories - RedTrailers.com
Bearing assembly part #30205 (your local bearing supplier should understand this number)
Seal part #30-52-10