I've been running Ultra Maverick rims for about 15 months. Over that time period I've managed to break 3 of the center caps seemingly just driving around normal. I know when they break because I start hearing a piece of the plastic roll around inside the cap. They are 100% plastic and only held in by 2 bolts. The plastic that catches the bolt head keeps breaking and allowing the bolt to pull all the way through.
As they have been breaking I've been running with just one bolt in them to keep them in place. This past week one of them broke on the other side leaving no way to reattach it (without some kind of mod).
I called Ultra to order a few replacement caps and they told me to call one of their retailers. I called the one they recommended and they told me the caps are $30 each. I had been thinking I'd order a full set of them given that I needed 3 anyway and they continue to break. After hearing that they are $30 each I passed. It seems ridiculous to me that at the current rate of failure I will be spending $120 a year on caps.
Just putting this info out there for anyone considering these wheels. They look great but I wouldn't recommend them due to the center cap issue I've been having.