Genuine OEM Audi Coolant Regulator End Cap, part number 059121484D. This cap seals the end of the coolant regulator, maintaining proper coolant pressure and preventing leaks within the cooling system. Constructed from durable cast metal, it weighs approximately 0.11 kg. Using a genuine OEM cap ensures a precise fit and reliable seal, critical for the long-term performance and safety of the engine cooling system.