This may (or may not) be useful for some of you out there. I'm 5'7" and weigh 140lbs. Size medium fits me very well. Not too loose and not too tight. Originally ordered a small but had to go through the exchange process for a medium. Price is high but I'm very happy so far. I hope it lasts a long time!
Good quality, wonderfull design.
Great fit and extremely comfortable. Not bulky or heavy, yet warm.