This very thin shirt isn't quite comparable in warmth to the midweight Duofold pants I pair it with, but it works a little better for me under a dress shirt (and I of course have the option to put on a warm coat).

This works best for me under a normal cotton t-shirt when I'm dressing for work. If I overheat a little, it's no problem: the material doesn't really retain sweat, so I don't get any damp spots, and body odor stays manageable.

I picked the gray color, thinking it would be a lighter shade than it is in actuality, mainly so I could easily distinguish from the white cotton tee's in the laundry basket. My mistake, the gray is quite dark -- enough so that it shows through any light-colored dress shirt. But it hides well under a white cotton tee.

According to Duofold's sizing guidelines, I should have chosen their size Large (me: 42" chest/36" waist), but I like a slim fit under my work clothes, so the Medium size fits perfectly. The Medium fits approximately the same as the Kirkland (Costco) Medium tees I wear.