Wheels are a major part of the exterior aesthetics of a car, even an immaculate example can be made to look shabby if the wheels aren't up to scratch.
The wheel centre caps on my 335i were looking a bit worse for wear, bubbling, corroded and dog eared from being removed a number of times. They were the older style too, showing the cars age.
Like most people I went straight on eBay and ordered a set of replacements, from a seller called asamuk2015, for the grand sum of £5.99 delivered. (Warning, read on to see why you should never order from this seller, or anyone selling fake centre caps).