Yes the M900 had the "sealed ceramic bush" jobs, not really worth paying extra for....
Well It seems the M900 wheels should be narrower than STX/Alivio replacement 8spd jockey wheels. M900 are the same width as 9spd jockey wheels, but with 10 rather than 11 teeth.
I'm now sorted after tracking down narrow 10t wheels.
Interesting. The early Stx where still on 7sp, only later did it go 8sp. And the 7 must have been wider as I remember having trouble trying the modify an 8sp version with the older parts. They where both the same tooth count of course. Would need to check if 'narrow' was on them. I wounded if you actually where given a 7sp version?
Something for a rainy day when I'm bored. Get them out and measure.
Ball bearing jockey, something that made m900 more expensive than 735. Worked well and a quick clean and service got the lower running again.
The top was the sealed ceramic, but that isn't ball bearing
Mine didn't seem to wear out the way cheaper ones did at the time.