Compatible with Shimano Hollowtech II or other 16-notch ∅44mm external bearing bottom bracket cups and 16 notch rotor disc lockrings (incl. E-Thru axle hubs). Fits Shimano BB Tool Adaptors TL-FC24 and TL-FC25. Specification Functions: 1/2" Dr. Material: CNC machined hardened steel. Size: ∅55 x 45 mm