Bad.GuerrillaCorrect, a size small would not fit you. Like most products from Alpha, these are replicas of military garments and are sized to be worn differently than most of us would wear them. Sizing down one size is typical on most of their outerwear. Fortunately, a size XS is available in both colors.
IanAndersonI'm also confused about the sizing. From the sizing chart, your model would choose a Medium or Large, but the Small size seems even a bit large for him. Is there another brand with similar sizing I could compare to?