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
Shimano UN55 Bottom Bracket - Santucci Cycles
Shimano BB-UN55 Square taper Bottom Bracket 68 x 115mm
Shimano BB-UN55 Square Tapered Bike Crank Bottom Bracket 68 x 122mm NEW - Walmart.com