Based on Joe's experience, I ordered the floating caps for my 2018 M550 with 668M wheels. Amazon just dropped them off, and I already installed them. I removed the factory caps off by sticking blue painters tape on them--they popped right out. Wish whoever knicked up some of the wheels removing the caps previously (CPO car) had done the same thing.
Removing and installing all 4 caps took less than 2 minutes. All spin exactly as they should, and there is nothing tight about them. They do feel securely snapped in place.
The package from Amazon is clearly a BMW original part, and is the exact same part as shown above. I can't see any explanation for folks having the floating caps not working on the 668M wheels unless they are ordering the wrong part or are receiving a counterfeit part. Or BMW had a run of 668Ms with a smaller than spec center bore size?
