SHIMANO XT HB-M8010 DISC ROTOR LOCK RINGLOCK IT UPCenterlock rotors don't use rotor bolts, they use a lock ring instead. The Shimano XT HB-M8010 Disc Rotor Lock Ring has outer serration and is designed to work with 12, 15, and 20mm axle hubs. They are sold individually. Features For use with 12, 15, and 20mm axle hubs Manufacturer's Part Number: Y2A598030UPC: 689228349506 | Shimano | Xt Hb-M8010 Disc Rotor Lock Ring Fits Hubs With 12/15/20Mm Axles