Bearings
 

I haven't played around xmods for a few years so what is the metal bearings for? :-?

they make wheels move faster and practically do what bearing do on any car, skateboard, bike, etc.....

this would be the best way to say how they work

http://en.wikipedia.org/wiki/Ball_bearing

Uh no, they don't make the wheels move faster. But they minimize friction and wobble between parts which makes the chassis more efficient and it will roll smoother.

actually you will have slight change in speed:)