Our socks are made from several counts of Certified Organic Long-Staple Cotton yarn from the U.S. and Peru. They also contain specially made cotton-covered Lycra and Natural Rubber. The Lycra and Rubber are used to aid stretch and durability and to ensure a good fit for a wide variety of feet. Our Lycra is entirely wrapped in cotton. Each sock label lists exact fiber percentages by weight, down to 1/100th of 1 Pct. Many other companies follow the suggestion of hosiery trade associations of NOT listing a fiber if it represents less than 5 Pct. of the total weight of a sock. Don't be fooled by socks that claim to be One Hundred Percent Cotton! All of Maggie's dyed products are made with the least amount of environmental impact possible, while still assuring color fastness and vibrancy. Initially Maggie's colors were all created with natural dyes. After we encountered repeated problems with color fastness and with heavy metal mordants used in these dyes, we switched to low-impact dyes in 1996. All of our dyes now meet or exceed the pending North American Organic Fiber Processing standards, which set specific limits for dyestuff, including metals allowed and discharge in effluent water. Maggie's Size Women's Shoe Size Men's Shoe Size S 5 - 7 1/2 M 8 - 10 4 - 8 L 10 - 11 1/2 8 - 10 Xl 12 - 13 10 - 13.