These ankle length athletic socks are not 100% cotton. 30% of their material is synthetic which is too much for athletic socks. Athletic socks need to have at least 85% of cotton. They are not so thin for the hot summer. They can be worn during fall and spring but not during the summertime when it is 85-90 degrees. The socks are very low cut, almost like no-show socks. I prefer regular ankle socks. As for the size they fit a narrow foot.