Genuine OEM Volkswagen socket head bolt, part number N91190801. This fastener is used to secure components within the engine cooling system, such as the thermostat housing or coolant flanges. It features a hexagonal socket drive, allowing for precise torque application in confined spaces. The bolt is manufactured to strict tolerances to ensure a leak-free seal when used with gaskets or O-rings. Genuine OEM hardware provides the exact length and tensile strength required for reliable engine assembly. Its specialized coating helps prevent seizing in aluminum engine components over time.