During the winter I like to wear long-sleeved T-'s and these really fit the bill.  I've tried several brands and these are my faves.  They're a very comfortable, synthetic fabric that is supposed to be moisture wicking.  How well they do that I'm not sure yet--I have to wait until I try them during the warmer weather and see how they do for hiking and biking.  They fit well, look good and again, are nice and comfy.  I recommend them highly.