(I already posted this in Engine Discussion, and someone suggested I put it here)
I'm starting to build my first remote control vehicle. The istructions call for a size 330 DC motor. I have been unable to locate a motor this size, in fact most of the motors I have looked at don't even say what size they are in that format. What I am wondering is; what does the number 330 mean? Is it the width, the length, or something else?
If anyone could answer my quandary that would be great.

Much thanks.
Ashman