I purchased and installed a complete set of sensors for my 2009 300C. The installer said it was difficult to spot them all, but he managed. This went on for about 20 minutes and the sensor in the car went on alert again. The right rear one was no longer connected. This went on for a few days and then it suddenly switched from right rear to right front, so I'm not sure if the problem is sensor-side or vehicle-related. He goes back to the mechanic to find out. I gave this 4 stars because I tend to think the problem is with the car and not with the sensors.