My car lost a couple of it's wheel nut boots and I decided to put my printer to good use. My wheel nuts are 17mm and these fit nice an tight once printed on my printer. I put them straight on without even smoothing and they look fine.

Let me know if anyone wants me to make a parametric version of this to support other sizes.

I wasn't really planning to upload this to thingiverse, so just did it quick. They fit and work so well I figured I would upload them in case they are useful to someone else. ;-)

Note: I added a custom support which should be snapped off after printing. I print these without any additional supports.