We've designed our sport bra sizing to be consistent with our everyday bra sizing; so, you don't have to find a new size. For example, if you wear a 34B in our other bra collections, we recommend that you choose a 34B (or alpha Size S) in any of our sport bras. The fit, itself, will be the same. What's different is the way a sport bra should feel: comfortable, but snug and super secure. No matter your cup size, excessive movement & bounce can lead to discomfort. That's why we design every MF Sea Sports Bra to compress and hold everything in place, reducing bounce by as much as 74%.