Genuine OEM Volkswagen socket head bolt, part number N91187801. This fastener is used for the secure mounting of components within the turbocharger and intake assembly. It is located at position 16 in the provided diagram. The bolt features an internal hexagonal socket drive and a cylindrical head. Genuine OEM hardware is essential for these high-heat applications to ensure correct torque retention and to prevent loosening caused by thermal expansion and engine vibration.