Genuine OEM Volkswagen Differential Housing, part number 2H0525121C. This housing encloses and protects the differential gears, allowing for variable speed rotation of the wheels. It is located as part of the differential assembly, indicated by position 1A on the diagram. The housing is constructed from durable cast iron to withstand the stresses of drivetrain operation. Genuine OEM construction ensures precise fitment and factory-level protection for critical internal components.