I have two other cotton Cosimas in size S but this time I decided to size down hoping to get more of a cinched waistline. I was worried about the arms holes being too small, but thankfully the smocking is forgiving enough and it worked out! The XS also seems a tiny bit shorter than the S so it’s a little bit better for my height (I’m 5’5”, 150lbs). I love the Cosima style because it’s effortless to throw on (I even wear them bra-less!) but looks very classy and it’s easy to style with a jacket/sweater/cardigan and statement necklace. And of course, it has pockets, which are non-negotiable!