They are all sealed and they are all ball bearings.
The scary part is I check the bearings every time I put a new tire on. They felt fine 4k miles ago. Of coarse I changed the other bearing and the sproket hub bearing as well. Figure they can't be far behind.
The quesion I have now is: How many miles are on that spare F4 wheel that is on the front of my bike. Hmmmmmmm. I guess it is cheap insurance to change those too.
02 919 (RIP)