The topeak external bottom bracket tool is designed for the installation and removal of external bearing cups its hardened steel design fits to a 12 drive ratchet making your job much easier and accurate than normal a must have tool for all workstations of budding riders topeak external bottom bracket tool features hardened steel engineering grade plastic includes crank preload adjuster for shimano cranks fits frac12rdquo drive ratchet 52x4cm 2pcs 1326g