Abstract: A master brake cylinder for an anti-locking hydraulic brake system is provided, comprising a central valve provided in each piston. The central valve comprises a first valve and a second valve. The opening distance A of the first valve is smaller than the opening distance B of the second valve. The first valve is made of a metallic material while the closure member of the second valve is made of a soft-elastic material, such as a rubber ring 40. Being made of a hard material, the first valve can perform a pressure regulating function, involving, however, the risk that dirt particles contained in the pressure fluid, are forced into the valve ball and the valve seat, respectively, thereby preventing the valve from closing completely. In such an event, at least the closing function of the central valve is performed by the second valve. To a limited extent, the second valve also can take over a pressure control function.