And these different shapes may find a better home in certain bra styles than others, so the system makes it a breeze to find a great fit. For example, those who might have less flesh at the top of their cup in a more full-coverage style (regardless of overall breast size) can use the sister sizing system to find a well-fitting demi bra, which cover half to three-quarters of a full-coverage cup, or even a push-up style with foam in a size that might not be their go-to for other styles. If you’re spilling out of your cups, Heer recommends a style with a larger cup style, like a T-shirt bra, a full-coverage bra (with little to no foam or lining), or a balconette (if you want to show off a little more cleavage), and use your sister size to find the most accommodating cup for your needs.