I am 6' and ~145 lbs. My normal fit is a Medium slim. I first got this parka in Medium but it was quite loose around the waist and shoulders and looked/felt bulky. I tightened the waist draw string which helped a bit but then it just looked like there was extra material in the middle, even when layering up.So I ordered a Small to see if it would be a better fit and it is perfect! Fits close to the chest but not tight, a bit snug in the arms but still room to layer and overall a more manageable size for my body type.In terms of insulation, this thing is WARM. I get cold easily and really like that I can wear this in 20 F windy, rainy weather with just a button up shirt underneath and be fine. I have to take it off as soon as I get inside because it gets hot real quick. The down seems to be spread fairly evenly and is really soft. Only complaint would be that sometimes it looks like very small amounts of down escape through the outer layer.