I am 5'4", 100 lbs and have a very small frame (30" bust). Bought an XS for climbing indoor and outdoor. It fits like a dream. I own a Prana Sabin top as well, but this one is definitely more flattering on smaller frames due to the lovely neckline and the back straps that will show off all your muscle. It is very breathable and stretchy. Can't wait to wear it outside!