Genuine BMW Rear Brake Pad Wear Sensor for BMW G80 M3, G82 M4 & G87 M2 vehicles, including the G81 M3 Touring & G83 M4 Cabriolet. Brand new, original, unused part supplied by BMW. When replacing brake pads, replace this sensor. Function of the sensor is to indicate to the driver when your brake pads are getting low.