Genuine OEM Volkswagen Expansion Tank, part number 3D0201301AA. This component is part of the engine cooling system, serving as a reservoir for excess coolant. It accommodates the expansion and contraction of coolant as it heats and cools, maintaining proper system pressure. Constructed from durable plastic, it is designed for long-term reliability. Genuine OEM parts ensure proper fit and reliable coolant system operation, preventing leaks and overheating.