I initially ordered a size L as I'm a 34D. The large fit well, but really wasn't supportive at all. I'd seen in one review that someone suggested sizing down for more support, so I returned the larges and got medium. Medium was a bit tighter but still fit well and didn't cut into my flab very much. But when I tried the jogging-in-place test.... Support hadn't improved at all. Honestly the support seemed about as good as a regular bra. It should be noted that I'm really not busty even though I'm a 34D, so I think that outlines just how low support this bra is. I think this bra would work for things like yoga or stretching or everyday wear, but I could never wear a sports bra which such low support. I unfortunately will have to return this.