I'm 5'11, 190 pounds and the medium fits me perfectly. I don't feel any irritation (although I wear a nipple band on all my runs). I just ran 20 miles in this shirt and it was great. Very light and really absorbs sweat. My other running shirts don't wick sweat as well as this one. I was going to order 2 more but it looks like they're sold out. Damn.