I bought the US small, im 5'8" about 160 lbs and it fits me perfect.  Had a few issues right out of the bag though... when i pulled the vest out of the bag the very top button fell out onto the floor, now for me this isn't a big deal cause i wouldnt button it up all the way to my chin.  The 2nd issue was the metal binder on the end of the draw string fell off also when i tried it on for the first time lol  this isn't much of a issue either cause it still functions.

The vest is pretty comfortable and just the perfect amount of warmth without a full jacket, we shall see if anything else falls off or apart.  Ill update if something else happens!