Shimano Dura-Ace SM-RT900 Centerlock Rotor Lockring and Washer Description: The Shimano Dura-Ace SM-RT900 Centerlock Rotor Lockring and Washer affixes your rotor to the wheelset via industry-standard centerlock threads. Sold Individually. Features: Designed for use with Shimano SM-RT900 centerlock rotors Centerlock disc brake rotor lockring fits most centerlock compatible hubs with a quick release or 12mm thru axle Internal spline accepts common cassette and centerlock lockring tools 40Nm recommend torque