Bought this for my 14year old daughter for her ski trip and it(along with a pair of Icebreaker leggings)kept her warm under her ski clothes. As with the leggings, the size is practically the same as the adult Icebreaker XS, but cheaper!, If anything, it is just a little shorter in length to the adult tops, but not overly. I love Icebreaker stuff as is warm and not scratchy, and really does NOT 'smell' easily - of course it will eventually, but only after a few days or more! Would recommend Icebreaker to anyone and everyone!