I am looking at two 6204 bearings at McMaster-Carr. One is a regular
double sealed bearing 5972K45 for $7.72. Another is a "PermaLube"
bearing 2349K423 that costs $15.32. According to McMaster, perma-lube
bearings are permanently lubricated and require no maintenance.

But what about the regular bearing 5972K45? If it is double sealed, it
must also have lubricant inside, already? What is different about these
Perma-Lube bearings?

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