The above photograph shows a standard B foot joint with a detachable
end which converts
For many years the C Foot Joint has been considered as "standard" with B foot joints (Bb Footjoints - rare) being considered as extras or as a special option.
In the UK the C foot joint is the most common option with many players
who need a B Foot Joint fitting it only when needed. In the States, I suspect
the B Foot Joint may be becoming or has become the most common option -
at least on higher quality flutes. Feedback required on this comment
The above photograph and notes are as accurate as my knowledge of the subject permits