Shimano SM-RT900 Lock RingThis Shimano lock ring is compatible with the SM-RT900 Center Lock brake disc. The aluminum locking ring is internally serrated. Washer included. Shimano SM-RT900 Lock RingThis Shimano lock ring is compatible with the SM-RT900 Center Lock brake disc. The aluminum lock ring is internally serrated. Washer included.REF: Y8PV98010