Shimano XT RT81 Centerlock Disc Rotors Aluminum spider. Includes standard type rotor lockring. Requires external-type rotor lockring when installing onto 15/20mm axle hub. 3-layer structure with aluminum core and two stainless steel outer layers reduces rotor surface temperature approximately 100 degrees Celsius compared to all-steel rotors. Hub/Disc Compatibility: Center-Lock Disc. Rotor Size: 160. Rotor Type: Two Piece. Pad Compatibility: All Pad Compounds.