Breasts for those who have them.
So in assisting authors to write more realistically, Size B is the average size of a Woman's breast. They do not jiggle when one walks. I only notice them when I run without a bra on.
As far as I am concerned, bras are the machination of satan.
A lady does not sit at the kitchen table and just pop a tampon into her vagina. It is most comfortably done in the privacy of a woman's bathroom, slightly squatting with knees spread.