Yeah, I'm not 100% sure how they work. I read there is a teflon coating in them in one google result. Might have to crack it open to see how it works. I've attached a picture of the original bearing.
I have a '93 Audi where the A/C compressor pulley bearing recently started to make a grinding noise. I realized it was the bearing and opted for replacing it, since I've done some pulley bearings on my newer Toyota.
I got the bearing out (not easily) and it's the original Japanese NSK bearing...