Measure the drive side , match that , to keep the crank set in similar place as you had on the bike first other side can be longer ..

Since you will only need a removal tool once, to take off the original fixed cup, assemble a Sheldon B's BB cup remover in the hardware store..

https://www.sheldonbrown.com/tooltips/bbcups.html



A Shimano UN26* style cartridge BB needs a different tool to install it.. *( there are even cheaper than the under $20 Shimano made ones to be found)







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