I just read it on another thread, and now I'm wondering what it is: bearing race. My guess is the angle each individual roller in the bearing is at and needs to be positioned at to spin in a perfect circle. I'm probably wrong, and you all know what results from assuming... so I figured I'd ask. Thanks!

There are two races in each ball/roller bearing. The race itself is the 'flat' portion that the balls, or in this case rollers, bear against. There is an inner race and an outer race. The outer race is pressed into the rotor, while the inner race is a part of the roller assembly.

So the inner race would be the one with the splines correct?

http://www.silicon212.org/roller.jpg

No splines.

Ohhhh, okay I got it now... thanks!