Genuine OEM Volkswagen Expansion Tank, part number 8V0121407A. This essential component of the engine cooling system is designed to manage the expansion and contraction of coolant as engine temperature fluctuates. It provides a reservoir for excess coolant and helps maintain proper system pressure, preventing overheating and damage. This translucent plastic tank features multiple hose connections and weighs approximately 0.591 kg. Using a genuine OEM expansion tank ensures correct material composition for heat and chemical resistance, precise hose connections for leak-free operation, and accurate volume capacity, all critical for the longevity and efficiency of the engine cooling system.