Fits great and is very flexible for any use!
I'm not sure if this review applies to the bikini top or bottom, so I'll comment on both. I wear a 36B size in a bra and the medium fits well and is super comfortable, except for the small stay wires on the sides. Not enough of an issue to return. I first ordered the small in the bikini bottom, as I wear size 4, but they didn't quite cover my flat butt. I returned and got a medium and they fit perfectly. Cabana Life does not have you state your weight in these review forms which I would find helpful... my weight is 128 lbs.
First I ordered a Medium in the top and it was too tight around the band, returned for a large- just perfect
Bottom, started with a small and returned for a medium for more coverage. Easy process for exchanges.