Genuine OEM Volkswagen Socket Head Bolt, part number N91176101. This precision fastener is used within the fuel injection system to secure the drive gear to the high-pressure fuel pump shaft. As indicated at position 5 in the diagram, it plays a critical role in maintaining the timing and operation of the fuel delivery system. The internal hexagonal socket allows for precise torque application during installation in recessed areas. Genuine OEM hardware is essential in this application to ensure the bolt can withstand the constant vibration and mechanical stress inherent in high-pressure fuel systems.