If you have to be on your feet a lot and are getting pain in your calves, these socks will cure that problem! Unlike some I've tried, they stay up. Order at least three pair to get free shipping. The foot part is thicker woven and precludes the necessity of wearing other socks over them.  I wear 9-1/2 size shoes and have fairly thick calves. The medium size is about right, and would fine for maybe up to size 10 shoe size. The thickness of one's calves is more a limiting factor than the foot part. The CoolMax keeps my feet from sweating. I hand wash them in the sink with mild shampoo, squeeze (not twist) the excess water out and they dry in a day or when so hung to dry. I'm am buying another five to have a week's worth.

[edit Sep 1, 2014 - I am up to 16 pairs of these now, in the three different colors. I don't wear any other sock. The first three I ordered are still as good as they were new--in fact, I've cut the feet off the first three to wear them on my calves when I sleep.