Center cap question

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From the searches i know this question is asked repeatedly, so forgive me, but I couldnt find a specific answer. i want to order some baby moon style hubcaps..heres what i have.

Front - 5 lug stock 15" steelies, it has four outside "nubs" on it, measures roughly 7 3/4" across..


Rear - 6 lug 15" wheel vintique smoothies, has three inside nubs on it, measures also 7 3/4" across..

am i going to have to order two different sets? i assume the front clip "over" and the rear clip "into" is that correct?

my camera is not with me at the moment..so if its hard to picture i understand. but any feedback is great thanks!