Window crank spacers 1968 Barracuda Fastback

Finishing the interior, I have three window crank spacers,
One is thicker than the other two.
See photo.
What is correct for my car, are the front and back different thicknesses?
Or are they all the same and somehow one got mixed in. I know I am missing one set of window crank-spacer, IIRC it is a rear set.