This Shimano Dura-Ace R9100 Bottom Bracket, utilising Hollowtech II technology, has smaller lightweight bearings and an advanced seal construction for smoother rotation and increased durability. Outside positioned bearings are for better weight distribution and more stability.. Series: DURA-ACE
. BB Shell Width: 68mm
. Bottom bracket with small ball bearings for light weight
. Advanced seal construction for smoother rotation
. Cups Material: aluminium with anodized finish
. Shell Material: CFRP
. Hollowtech II - Threaded BB type