These shirts are thin cotton, but very soft with good stretch for movement. Great shirt for warmer weather or when you need to move around a lot. They run small and then shrink in the wash. I ordered 2 full sizes larger, and after washing and shrinking, it's perfect.
I know some people might be put off by the sizing, but Harry's had large sizes so ordering 2 sizes up wasn't an issue. And, I took heed from the other reviewer to do so. I still give the shirt 4 stars, because it's very soft, feels great against my skin. Even though it's a thin cotton, it seems cut well. I've washed it several times already, and it shrank evenly, so it's a sizing issue, not bad design.