I'm 5'2" and usually run between a small and a medium (US size 6/8). Description says that this has stretch but a lot of the reviews said that it runs small so I decided to order up anyways. The medium barely fit and the slit was so high, I ended up with a large for the event (I had time in between receiving the package and the ball to be able to make a return). Also note that the armpit hole was a bit tight for the medium as well. The quality is really nice though, so I ended up happy regardless.