I'm 5'6", 125lbs, and I got this in a size small in the color black. I purchased this expecting it to fit exactly like the tri-top, just with a layer of cotton on the interior, but not so much. It slips down a lot and doesn't bind as well. It is nice and soft, but it's just not worth it if you actually want a good bind (I have a small chest size as well, somewhere around a small B?). You're better off just wearing something cotton underneath the regular tri-top (I usually either wear non-compression cotton sport bras or I hem undershirts shorter to wear underneath.