XIKE 10 Pcs 6901ZZ Double Metal Seal Bearings,Pre-lubricated

These bearings came in a plastic tube with a cap. Each bearing is stamped with its number on both shields plus the inner race face is laser marked with the manufacturer’s name, bearing number and bearing ID, OD and width. The bearings are smooth to rotate and show attention to detail.

I decided to check the OD of a few bearings to see if they comply to ABEC 3 specification. For the 28 mm diameter the OD tolerance should be 0 to -8 micrometers. Different bearings showed different measurements, but for the same bearing the roundness was within 6 micrometers. It may not be good for industrial use, but for me it would be OK.

This bearing has non-contact metal shields and grease lubrication. The limiting speed is listed as 20000 RPM. But a similar 6001-2RS bearing with rubber seals also shows the same limiting speed. Usually the bearings with metal shields have higher speed limit due to no rubbing. I sent this question to the seller and also asked why the speed limit is so low. I did not get any reasonable answer.