Shimano ultegra 6800 bottom bracketthe shimano ultegra 6800 bottom bracket is a threaded bb designed to work with hollowtech ii style shimano road chainsets.featureshollowtech ii integrated bottom bracket uses a wider bearing placement and larger axle diameter for increased stiffness and efficiencyhollowtech ii integrated bottom bracket seal design has minimal bearing interface ensuring smooth rolling and increased durabilityuse the tlfc37 or tlfc25 spanner adaptor tool in conjunction with the tlfc36 standard shimano bb spanner for installation and removalcompatible with all shimano hollowtech ii road cranksrevised sealing system reduced drag by 50%note tlfc37 or tlfc25 spanner adaptors are not includedspecificationsmaterial aluminium cups steel bearingsrecommended use road cycling and racingshell type externalthread english bsa or italianshell width 68mm eng or 70mm itaweight 77gbuy shimano components from chain reaction cycles, the world's largest online bike store.