These caps are great! Installed them today and they complete the darkened theme. I order caps 21-23mm and they fit over the original tabs. We reused 20 or 24 tabs because we felt the standard tabs covered the tapered bushing better than the regular slotted locking tabs. For safety reasons, we have retained a locking lug on each wheel. These caps took a little elbow oil, but the tool helps a lot. The hook on the end of the tool helps slide the edge of the lid onto that particular ledge. Then simply press the bar with two fingers until it clicks into place. They fit well so I don't think they will fall off if not put on properly. Good luck and I will buy a smaller size for my lock keys!