Genuine OEM Volkswagen Master Cylinder, part number 0XW721388. This component is responsible for converting the mechanical force applied to the clutch pedal into hydraulic pressure. This pressure is then used to operate the clutch slave cylinder, engaging or disengaging the clutch. The master cylinder has dimensions of approximately 183mm in length, 85mm in width, and 70mm in height. Genuine OEM master cylinders are critical for maintaining the correct hydraulic pressure and ensuring smooth, reliable clutch operation.