i am wanting to change from a factory plastic spinner to a polished aluminum spinner, how does one measure the spinner in order to purchase the correct one? Thanks for any help.</p>

It can depend on the type of plane and the engine/motor you have. The main thing you need to get right is the thread size of your engine/motor shaft. Most .46 sized glow engines have a 5/16" fine thread (24), many brushless electric motors are metric, so this is the most important thing to know. The diameter of the spinner itself has more to do with the plane you are using. A sleek speed plane might look better with a smaller spinner where say a .46 sized T-34 will look better with a 2 1/2". Most .40/.46 sized planes will use anything from a 1 1/2" to 3" spinner.

measure the distance the spinner plate will occupy.

THANKS GUYS!!