Genuine OEM Volkswagen Clutch Master Cylinder Seal, part number 1K0721741B. This seal is designed to prevent hydraulic fluid from escaping the clutch master cylinder, thereby maintaining the necessary pressure for the clutch system to function correctly. It is indicated as part 17A in the clutch system diagram. The integrity of this seal is vital for preventing leaks and ensuring smooth clutch engagement. Genuine OEM seals provide the exact fit and material properties required for reliable hydraulic sealing.