The Shimano UN300 English Bottom Bracket High quality sealed bottom bracket with a squared taper. The new chain line stabilizer helps to increase chain reliability. The adapter material is extra strong Aluminum. For use with JIS square tapered crank sets. The spindle is hollow and crankarm fixing bolts are sold separately. Available in Shell lengths 68mm or 73mm. Available in Spindle lengths 68mmx107mm, 68mmx110mm, 73mmx113mm, 68mmx115mm, 68mmx117.5mm 73mmx118mm, 73mmx122.5mm, and 68mmx127.5mm.