I don't get what band size has to do with breast form size, Steph? Bras, YES! Silicone forms, NO! They aren't usually sold that way!
Usually it's: B, C, D, DD, etc. Or, 7, 8, 9 ,13, etc.
And, if u like B's, GREAT! Especially if they're REAL!
I'm 5' 10" and about 150. I normally wear C's or D's. THAT depends on my figure, as well as the outfit I have on!
In a slim, sleek outfit, wearing small hips/butt; it's C's! (As in my avatar!)
When I'm showing off my figure in corset and big hips/butt; it's D's or DD's!
When copying teens I go down to B's! "Big girls"? Up to H's!