Our Hiker/Biker Sock is named after Killington Mountain in Vermont. The president of Maggie's hiked 6 miles to the top of this mountain and she found that the original samples of these socks SAVED her feet! Contents: 70% Certified Organic Merino Wool, 29% Nylon, 1% SpandexWashing Instructions: Machine Wash Cold, Line Dry Sizing:Medium = women's US shoe size 5-9 & men's US shoe size 4-7Large = women's US shoe size 10-13 & men's US shoe size 8-12Color:Black = Black and natural speckleGreen = Olive green and natural speckle