BB-UN55 vs BB-UN300 - which is the better square taper bottom bracket? - restoration.bike
NEW SHIMANO BB-UN55 70 x 113mm Square Taper Bottom Bracket Italian 36 x 24 tpi | eBay
What is the difference between this Shimano BB-UN50 and the BB-UN55 ? The former is hard to find for sale, the latter seems to be found everywhere : r/bikewrench