Shimano BB-UN55 BSA Bottom Bracket Set Matte Black This electronic-shifting platform features the

This electronic-shifting platform features the Shimano Ultegra Di2 8100 groupset and full internal cable routing

a simple and reliable built-in service solution without disassembly of the seatpost

dual seals

stiff enough to resist significant flex whether you're pushing or pulling hard at the pedals

Atlas offers greater articulation

Shimano BB-UN55 BSA Bottom Bracket Set Matte Black This electronic-shifting platform features theThe Shimano BB UN55 is often cited as the gold standard for square taper cartridge bottom brackets. It combines high quality sealed cartridge bearings with a hollow spindle to deliver exceptional durability and smooth pedaling. This unit is a favorite for commuters and touring cyclists because its "set and forget" design requires virtually no maintenance once installed. Built with a sturdy metal left hand cup (unlike the plastic versions found on