I have an 2002 SLK 230 R170 and so as I miss the rear parking sensors built in on my recently sold 2007 C180K I purchased the (UK) Fensens rear parking sensors. I can confirm that following discussions with Fensens concerning the shape of the bodywork close to the rear number plate the Fensens rear parking sensors work really good. They operate wirelessly via Bluetooth direct to a free App that shows the rear of the vehicle in a diagram with colour coded "waves" when getting closed to an object on your smartphone. I have not bothered buying another one for the front of the car as the front is too curved to be able to install the Fensens correctly. Having said that maybe someone else has had a go and made it to fit the front? Thought you should all know if you miss the rear parking sensors and don't want to get involved with cutting, drilling or wiring sensors in to the car.