Well, let's see - yep those smaller ones slip right inside the wheel.
I tried it, bought the about-3-inches ones from somebody.

I agree, about 3 1/4 inches for outside diameter.
Maybe 3 3/8 to be more precise.
(for the older 14 inch bundt).

And as for why... just need to replace missing ones where the tabs broke off,
then the cap fell off on the highway.

I do not have concourse level cars, I am just glad the paint matches.
Don't need new caps, not looking to improve, just replace missing ones.

So used caps are fine , I spray paint what I need to.

Anyway, thank you everyone for chiming in.

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80 300D 340K Owned 30 yrs
83 300SD 440K Owned 9 yrs - Daily Driver 150mi/day
02 Z71 Suburban 117,000
15 Toyota Prius 2600 miles
00 Harley Sportster 24k
09 Yamaha R6
03 Ninja 250