Love this jacket! I'm 5'2"/105lbs/32B and I got the small. Looks great - I don't look like I'm swimming in the jacket nor do I look like a michelin man (yay!). I can fit more underneath if I really needed (I tested out with the archteryx atom LT xs, patagonia r3 just to see what I could get away with but in reality, would be sweating) but I've also worn it with just a single L/S shirt underneath and it looks/feels great. It's windproof and warm! Love the insulated hood that I can actually wear over my ponytail. To make it waterproof, I can also wear it underneath my marmot minimalist jacket (xs).