Among the many bottom bracket standards in the bike industry is BB86. Where a typical road bike has a 68 or 70mm bottom bracket shell width, a BB86 equipped bike has a shell that measures 86. 5mm wide. This gives frame designers a little more room to get creative with frame design and improve stiffness at the ever-so-critical bottom bracket junction. This Shimano Dura-Ace SM-BB92-41B Press Fit BB is made to press right into your bike. It will mate your Shimano Hollowtech crankset to any frame equipped with a BB86 bottom bracket shell. It includes two steel cartridge bearings pressed into composite cups. The cups increase the outside diameter of the assembly to 41mm to match the inner diameter of the frame's bottom bracket shell. There is a 1. 75mm thick outer lip that provides a positive stop for the cups when you press them into place. Shimano includes their standard plastic o-ringed inner sleeve to protect against water damage should it find a way inside your frame. It also comes with black plastic dust shields that snap into the inner race of each bearing to keep out dust and debris.