As others have stated this jacket is fitted so will be 'smaller' than a regular (non-fitted) windbreaker type jacket. That was fine with me but the weird thing - the sleeves run long. Why have a snug jacket but extra long sleeves? Eh, annoying but not something I'd return the item for. I'm 5'6" 120lbs and ordered the medium which fits well over regular shirts and sweaters if they're not too bulky.