I ordered a small and it fit perfectly. I usually wear medium, so it might run a BIT big (but not too much; I'm 5'7"). It kept me warm and sweat free on a long x-country ski. Perfect, even in cold weather.

Light, breathable windstopper softshell
This pullover is perfect for active pursuits when it's yucky outside. I've had the transition vest and have taken it on every single one of my alpine climbs, and this pullover is basically the same as my vest but with sleeves. It is a thin, stretchy windstopper softshell. Completely windproof and extremely breathable. The stretch makes the fabric feel even better. My vest had a lot of areas that were non-windstopper, but this pullover is almost 100% windstopper. I love it so far. With a thin base layer underneath, I can use this for everything - running in the cold, alpine climbing, snowshoeing, backcountry ski...everything! The fit is normal to slim. Sleeves are a good length and the sleeve cuffs fit well. The only downside is that the stitching / seams are a little rough, but I would never wear this without a base layer underneath so it hasn't bothered me at all. Overall, absolutely love this pullover.

Awesome top!
This is another great products from MH. I love the windstopper on it. I just wear it over a light smartwool base layer and I am set for snowshoeing, and xcountry skiing. You can use it for other acitivities. It is a great product, at an outstanding price.

I love this shirt
I wanted this shirt for an upcoming hiking trip, but also for riding my motorcycle in cold weather. I've worn it walking on high wind days -- it blocks the wind and breathes so I'm warm at the start and not hot at the end of the walk. I'm a pretty standard size 6 except for short arms and the Small is a perfect fit. The articulated arms and the shaping of the shirt are very comfortable.

Windstopper
I loved this shirt, its the first Ive owned made from the windstopper material. Its great, I have a windbreaker which I thought was ok until I wore this shirt and havent felt the wind since. Love it!!