The shirt has a nicely tailored shape for a thin torso. Medium fits a 6'1" 160 pound frame well. The size guide suggests a Medium has a 40 inch chest, and I have a 41 inch chest, so I almost got the large, but was glad I got the medium -- there is still enough room in the chest to move comfortably.The fabric is very thin, which works for me because I am wearing it to an event in Miami in July. But, yes, you can see my pink skin tone through the shirt in bright light. Don't expect this shirt to obscure any embarrassing tattoos. Fabric feels quite breathable and the tag says 70% cotton, 25% nylon and 5% elastan. Fabric does not feel stretchy.