Reservoir bolt. W/E-GOLF. A threaded rod with a drive head (such as hex, 12 point, torx, etc.) on one end used to secure the Brake Master Cylinder to it's mounting point. Brake Master Cylinder Screw. Master Cylinder Reservoir Mounting. Secures the master cylinder reservoir to the master cylinder. Screw. Included with: Booster assembly, Master cylinder assembly, Master cylinder assembly Part cannot be reused/reinstalled, Master cylinder assy, Servo.