Genuine OEM Volkswagen Self-Locking Collar Nut, part number N90928802. This nut features a built-in locking mechanism, often a nylon insert or deformed threads, to prevent loosening caused by vibration. It is located at position 14 in the diagram, likely securing a component on the rear door assembly. The self-locking feature is crucial for maintaining assembly integrity in dynamic environments. Genuine OEM self-locking nuts provide the specified locking torque and durability.