Providing added stiffness and weight savings, the BB30 system is offered on a small, but increasing number of race worthy road frames. The problem lies in compatibility with Shimano's popular cranks, such as Ultegra and Dura Ace. That's where the Wheels Mfg BB30 Adapter For Shimano comes into play. This nifty solution fits Shimano road cranks to BB30 equipped frames, thanks to its two reducer sleeves that precisely press into the BB30's bearings for wiggle and creak free performance. Please note that this adapter works with all Shimano and Shimano compatible road cranks with a 24 millimeter spindle.