I think the part that "lives on the bike" actually sits on the shell, with the lock ring holding it in place.
You think it goes over the bb shell rather than in where a bb spacer would go?
Might make (slightly) more sense but the od of a bb shell must be pretty variable depending on material etc.
@M_V started
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I think the part that "lives on the bike" actually sits on the shell, with the lock ring holding it in place.