Hike yourself up a peak, work up a sweat, but you wont freeze when you arrive at the summit....because you were smart and packed your Houdini! Blocks the wind so you can fully enjoy yourself. This is an essential piece for hiking, running and climbing. Fits in the palm of your hand. I am 5'7" 118 lbs with a 34 bust. I ordered the medium as I wanted some extra room for mobility and glad I did.