After a number of purchases of bearings from likes of Amazon and eBay it was obvious that sellers are passing off poor quality bearings as precision items. I’m posting this as I’ve actually found a really good value high quality bearing from Amazon UK.
On the right is the usual junk, loaded with thick sticky grease (probably to mask the excessive play and quiten them down), also notice the bore is not ground and the balls are not polished, in addition the rubber shield is a poor quality plasticised moulding.
Compare that to the one on the left which appears to have lithium grease, highly polished balls and all ground surfaces. The shield is metal with a rubber over moulding and marked ABEC9 but I doubt that it this price point
No connection with the seller, they can be purchased 8 for GBP5.09: