Genuine OEM Volkswagen Coolant Reservoir, part number 5Q0121407A. This component stores and regulates the engine's coolant fluid, maintaining optimal operating temperature. It is located at position 20 in the cooling system assembly. The reservoir is constructed from durable plastic to resist coolant and temperature fluctuations. Genuine OEM reservoirs are designed for exact fit and proper sealing, preventing leaks and ensuring the efficient operation of your cooling system.