What is the meaning of letters 'B', 'C' etc., in women bra sizes

Why 9 Bra Sizes All Fit - Hurray Kimmay

How does bra sizing work? 3 key points to know (3 minute read

Bra size - Wikipedia

Which hook on the bra does the band size refer to, innermost

Bra size - Wikipedia

How Bra Sizes Work: A Full Guide

Came across this quick guide on r/coolguides. Is it just me, or

Why do bra sizes have letters in them? - Quora

Which hook on the bra does the band size refer to, innermost