The bottom bracket is a component that usually does its job without making a fuss, and Shimano knows how indispensable it is to our drivetrain, which is why they ensure smooth bearings, advanced sealing, and high manufacturing tolerances. With the Ultegra SM-BB72-41B PressFit Bottom Bracket, we're able to press this component right into our frame, working with our Shimano HollowTech crankset and any frame equipped with a BB86 bottom bracket shell. Two steel cartridge bearings are featured with this bottom bracket, and they are pressed into composite cups which increase the outside diameter to 41mm to match the frame's bottom bracket shell. A 1. 75mm thick outer-lip provides a positive stop for the cups when they're pressed into place.