4.2 LITER. RS4. Vibration damper bolt. A threaded rod with a drive head (such as hex, 12 point, torx, etc.) on one end used to secure the A Pillar to it's mounting point. Engine Harmonic Balancer Bolt. Body A -. Engine Harmonic Balancer. Hexagon socket head. Inner. Torx screw. Vibration damper. Included with: Windshield frame.