The two machined aluminum cups thread together ensuring the bottom bracket remains stable in the frame, increasing bearing life, and simplifying maintenance. This means no more creaking, smoother operation, longer bearing life, and really quick bearing replacement. Specifically designed for installing 24. 00mm spindle diameter cranks (Shimano, Etc.) in Cannondale BB30A (42mm ID, 73mm wide asymmetrical BB shell) frames without the need for any adapters.