The product is a used 2011 BMW X5 3.0L Diesel Rear NOX Sensor with Control Module. The sensor has the Manufacturer Part Number 858984401 and is a genuine OEM part from BMW. It is specifically designed for the rear placement on the vehicle, and includes the necessary control module and sensor for installation. This sensor is a crucial component in the Diesel Exhaust Fluid System, ensuring proper emissions control and performance for the BMW X5 model.