The BB-UN300 square taper bottom bracket was launched by Shimano as successor of the models BB-UN26 and BB-UN55. It covers a wide range of applications, from Touring and City bikes to older Road and Mountain bikes. BB-UN300 is available with BSA thread and in different axle lengths. In this type, the bottom bracket axle and crank are connected by a square taper. Does not include crank bolts.

SHIMANO - Square Type Bottom Bracket - MTB - Standard Structure