Centre Cap Question

[wfcmeady]

Are the centre cap diameters relevant to the car or the alloy (aftermarket)?

Probably a silly question, i just don't want to get it wrong.

 

[Jat_172cup]

alloy im guessing mate :S

 

[wfcmeady]

Hmm, s'pose you're right, was kinda hoping there would be a general size.

Cheers anyway.