Cut downhill speed up to 49 without using wheel brakes Saves brake wear - and - tear. Computerized brake controller, safe, reliable operation. No maintenance. Banks' revolutionary design produces stronger braking power than other exhaust brakes. The large - bore housing, streamlined to increase airflow and diffuse exhaust, adds to engine power when Banks Brake is inactive. Banks engineered in a timed valve closure rate to prevent backpressure spikes common to other exhaust brakes and provide smooth operation. Every unit is factory tested and never requires calibration. Note SmartLock required on automatic transmissions. US Patent 6,152,853 A