I am 5'6", 121 lbs, 34B and got this in XS in white and black and also S in white. I wear either size in Athleta clothing, depending upon the cut of a given garment and how I want it to fit. I have one complaint about the white jacket - that the pocket zipper pulls are black, not white like on the w...ebsite. I definitely want them to be white or, at least, silver like the main zipper pull. But I like the jacket so much otherwise that I'm overlooking this for now. Hopefully they'll fix this. The XS fits like a glove, snug and figure-flattering. If you want a looser fit or have longer arms or a bigger chest, size up. While this fabric is ribbed, it looks much like a micro-pleat at first glance. The fabric is spring/fall weight. The princess seaming is very slenderizing - more narrow at the waist. It looks fabulous with tights. The sleeves on the XS are a perfect length for my arms - not too long and not too short with my thumbs in the thumbholes. The sleeves on the S are too long for me but I got the S to wear over looser or thicker tops. The S is looser throughout both the arms and the torso (fits more like on the model), but the princess seaming keeps it from looking frumpy - it just looks a tad more relaxed and goes better over jeans. I like that the jacket has no hood, as this makes it more classy-looking. I definitely recommend!