Sweater tank top

I love the color of this top, and when I saw it online, I ordered two - one in the blue and one in black. I'm 5'3" and about 138 lbs, 34C cup. Normally, the Medium fits perfectly. But in this case, the size Medium was too loose, not a little, but enough for me to return both tops and exchange them for a size Small. The Small fits just right. The Medium was too loose and the armholes were too deep. The quality is very good and the blue is vibrant - just what I wanted! I think it will look great with jeans, leggings, or more dressed up.