Axle Diameters

What is the diameter of a typical dually axle? Is there different diameters between chevy/ford/dodge? Ima start making dually specific tabs.

I think 4", I can measure tonite when I get home for a dana in a square chevy.

Most Chevy's are 3.5-4" and I have a Ford in the back that is 5.5".

I know my C&C's was different from the stock rear.

Kewl, does anyone know of any sites offering tabs for duallys? One of the things i hate most is having to make tabs by hand so i wanna offer as many sizes as i can.