Genuine OEM Volkswagen Toothed Lock Washer, part number N10772901. This washer is designed with internal or external teeth that bite into the mating surface and the underside of the fastener head, creating a tension that resists loosening caused by vibration. It is used in applications where a secure, vibration-resistant connection is critical. The toothed design provides a positive locking action. Genuine OEM washers ensure proper material hardness and tooth design for effective locking.