Trailer bearings

[ModelA29]

Timkin has bearings made to their specs in China. They have QC there and also here where they check (a sample %) that they meet all specs - size and metallurgy.

Brand X sells a similar ChiCom bearing but without the extensive QC - you take your chances when it arrives from ebay.
Clean and inspect your current bearings - any pitting on the surface means they are dying. If they are still smooth relube them and go another 10-20,000 miles.