not true. an unsealed american BB will use the same size cups as a sealed american BB but the way the cups are made is different. you cant use sealed bearing in cups meant for unsealed bearings and vis versa. sealed cups are meant to hold a cartridge bearing, unsealed cups are meant to hold caged ball bearings with grease and all. this means he would have to change the cups when switching to a sealed BB even tho they're both the same size.

amp27, this will help you: http://www.danscomp.com/serve.php?se...bb_diagram.htm