I love this shirts as under shirts. I sweat a lot because of my diabetes and the ridiculous humidity we have here.
This shirts, don't ask me how, keep me dry. No sweat spots, no stains. They fit well, usually I am a double xl guy but xl does fit well. They are long enough (me being 6.2) not to show the whole world the moon.

So if you area bit on the sweaty side, try them. They solved quite a problem for me.

I also have them in white and left a opinion there too. I own 8 pairs btw.