Master cylinder seal. A round Ring used to seal between the Brake Power Booster Unit and it's mounting surface. Brake Master Cylinder Gasket. Brake Master Cylinder O-Ring. Part cannot be reused/reinstalled. Power Brake Booster Gasket. Power Brake Booster Seal. TO. Power Gasket. Seal. Vacuum hose o -. Included with: Master Cylinder, Master Cylinder Part cannot be reused/reinstalled, Master Cylinder assembly.