Great wool shirt.
Good fit, slightly tight - but as a layering piece it should be. 5'10 160 and not so tight I can't wear it around as a nice shirt. Great warmth to weight ratio and all the other perks of wool.

I'm 5'3" and a 37" chest, 135lbs and the small fit me very well, the only problem I had was the material which I had hoped was a little thinner. This particular fabric felt a little thicker (somewhere in between a sweatshirt material and thick cotton t-shirt) but the stretch and feel was very comfortable, not itchy at all.

Love it
The design is close-to-skin so there's less room than a typical shirt but at 5'10" and 195 lbs it's not tight on me either. I was expecting "Midweight" material to be thicker but it's thickness is like normal t-shirt material. I love the design and style.

Smartwool zip Ts
I have owned a lot of clothing for outdoor activities, but I remain a wool user. Smartwool is the best next to skin fabric made. These layering garments will produce comfort like nothing else. Not too tight so that you get no abrasion of exposed parts or hair pulling (chest hair), and close enough to wick you dry and keep you warm. I own several zip Ts of different weights for different temps. The midweight one is good for significant cold, or for use with fewer layers. When outside, the zip t makes a turtleneck, helping to keep your outer layers clean as well, such as the neck on your down coast/sweater. You can wear it for a couple of days as well. Great stuff. Get some of everything.

I love smartwool tops more than life itself..
I live in the frozen tundra known as Massachusetts, and I found these smartwool tops to be the best tops ever. They are warm, versatile, don't smell, they breath. I am happy as a clam at high tide. I wasn't digging the women's colors, so I bought a men's medium (I had the women's large) and it fits just fine. I have to get another one the way this winter is going.