1% Spandex, 3.5% Nylon, 16.5% Polyester, 80% Cotton (I know, that's 101%- I'm just going by the label) and made from Honduran cotton by Hondurans.
Stretchy but not too stretchy. Soft but not as thick as winter socks. No loose threads or other indications of shoddiness. They are comfortable with no  inside seams assaulting your toes.
I can't find a single thing not to like about these comfy socks.