Genuine OEM Volkswagen Engine Coolant Tank, part number 5QM121407C. This reservoir holds excess engine coolant, accommodating volume changes due to temperature fluctuations and providing a reserve for the cooling system. Weighing 0.433 kg, it is designed for durability and proper fluid containment. Genuine OEM coolant tanks ensure proper pressure retention, material compatibility with coolant, and accurate level sensing for reliable engine cooling.