BOX Box Two 24mm Bottom Bracket (68/73mm) - BlueFeatures cold forged and CNC machined alloy cups, dual labyrinth bearing covers and precision sealed bearings Designed to fit all 24 millimeter crank spindles and frames with 68 or 73 x BC 1. 37 inch bottom bracket shells Compatible with Box Three, Box Four, Shimano HollowTech II, and RaceFace X Type 3rd party web sales must be an Authorized Dealer TECH SPECS spindle interface 24mm shell BSA shell ID 33. 6mmx24tpi width 68 73mm color blue