Shirt is comfortable and keeps me dry. Ran a race in 20F degree weather and it kept me dry, therefore warm.( I had a light workout jacket over the top.) I say it is American sized because I normally wear an XL in most tee-shirts. I wanted this one a little closer to the body so I ordered a L. It is a bit more generous than I expected so it fits like a large is supposed to. If I would have ordered an XL as I normally do, I would be swimming in it. However, that is not Champion's fault, that is most other manufactures trying to get by on the cheap. I will order more.