it was an electromagnetic parking system which uses a strip of foil to be stuck inside the plastic bumper. I had both my bumpers off at one point and it was easy to fit, I put the front one inside the diffuser section and the rear just across the middle of the bumper. There is no external evidence of them being fitted. They are sensitive to salt water getting at the foil in the strip and I have had to paint over the foils a couple of times in the last 5 years to stop them going crazy in the wet, but generally they work. I put a distance display thing on my rear view mirror which i hated at first and now dont even notice, and its good for reversing. I will drag out the exact make when i get home but it was not expensive to buy (£50 i think) but required a bit of work to get all the wires in place. I fitted an additional button on the dash to power up the front sensors, you have to switch them on before you front park, reverse just uses the power from the reversing light to enable them. Drilling a small hole in the leather for the button really freaked me out, but it was small and I got over it!!