Like other reviewers, love this as a lightweight layer you can chuck on in between or over other layers when it really gets cold in the winter or just need a layer on a summer eve. Folds into tiny pouch, no bulk and effectively reduces wind chill. At 50kg and a size 8-10, 30 inch chest and 29 inch waist, the Small fits just right, room enough to go over mid layers, not too much room that it's too baggy over a tee shirt. Best piece of kit I've bought in ages, esp for the winter.