Shimano Dura-Ace BB-R9100 Bottom Bracket In the newest edition of Shimano's top end component group, the bearing of the Dura-Ace bottom Bracket, the bearings are positioned to the outside to provide better weight distribution and more stability. This years model has slightly smaller bearings which allowed the shaving of a few grams. Features New improved sealing ensures 50% less drag Available for English and Italian Threaded Bottom Bracket applications | Shimano | Dura-Ace Bb-R9100 Bottom Bracket English Threaded (Bsa)