I was out shopping the other day with my wife. We were in the lingerie section and she saw a bra that was a 30C. She said, "that is not a C cup, it's way too small." I said, "That's because it's a 30 band. A C cup on a 30 is not the same as a C on a 38." She said, "What are you talking about?" So I proceeded to explain that that 30C cup size would be a would be the same cup size as a 32B or a 34A. That as you go up a band size, you go down a cup size. I pointed out that if her 38D was too tight and she went to a 40, she would need a C. She looked at me like I was crazy, so I told her to look up sister sizes.

What made the exchange even funnier is, from the start, bras have not been allowed. She has said she thinks I probably have one, but doesn't want to see me in one. I'm guessing after that conversation, she's sure I have one.

Later, I told this story to my best friend, a GG, and her response was, "I didn't know that either."

So, my question is, do only bra makers and CDs know, or care, about sister sizes? Based on my limited research, 100% of GGs have never heard of them. lol.