It is always a good idea to buy a set of 5. What if you bought a set when they still made them in 17" and you smashed one on a curb or busted it at the track, "out of luck" we only make them in 18" and 19" now. I don't know of a knock-off that looks very similar, but there must be something close. It's hard to spend $600 per wheel and get a set of 5, but it is worth it in the end. Those are still one of my favorite wheels. Hope you find something that works out for you.