Versatile as top or base layer
This was purchased for my niece. Here's what she had to say: "This shirt is a great top layer for a run on a chilly summer morning. The size small is form fitting (for reference I am 5'6'', 112 lb) and the size medium is a little looser. Both sizes would work great as a base layer in the winter, but the size small could go under my dress shirts and keep me warm at work without being detected. The fabric is soft and surprisingly lightweight for something this warm. I'd expect nothing more from Smartwool.