I am a 34C and I ordered a D cup thinking it would fit fine.  It was so small!  it looked like a B cup bra.  I was able to get it on comfortably but it left indentations in my breasts--not flattering.  I then tried it on a bit higher and it looked smoother but provided no support (it actually made my boobs look saggy; and I do not ave saggy boobs!).  It might work for a small C cup and under but it is not for shapely breasts.  The good thing about this product though is that it is super sticky and it doesn't feel like it will fall off.  It is also thick and the cups were the same thickness and same size-just small.  I may hang on to it for when I wear baggy lace back shirts but it is not to be worn with tight clothing when it is too small.