I have noticed that I have one center hub cap missing and I am planning on getting a replacement. Probably a used one. Question: which is the right one for my Focus? I have a 2001 ZX3 with 16" alloy wheels. Any other information needed?
To answer your question, as long as it looks like the same one, there are no major differences between styles of center caps. In other words, 15" rims had much larger center caps that cover the lug nuts while the 16" rims had just small caps to cover the hub. You can easily tell the difference between the two.