This is a good, all-around base layer. The positives right away:  I am very happy with the materials, fit and quality. Definitely take the manufacturer's advice and order a size up for a "regular" fit. They are just slightly thicker than something like UA's "heat gear," but definitely thinner than something dedicated to keeping you warm. These would work well under a pair of shorts for a cool spring or fall run, or under some pants for that little bit of extra warmth in the winter. If the temperatures got down into the 20s, I'd look for something warmer. My only negative is that the bright stripe details shown in the picture are actually the stitching, and the color is much more subdued than I was expecting. Other than that, totally happy.