I was a small B and hiding it sufficiently with a sports bra. I guess it depends on your frame and what you're carrying on it (how much fat and muscle.) I was about 10 pounds over my "weighed all my life weight" of 150. Too much time at a desk instead of working in the field. But the sports bra seemed to work well enough. However, I was asked once or twice if I was working out. You know, all that new chest muscle. 😀