SealSkinz socks have a patented fabric structure of three highly engineered layers including a membrane capable of allowing perspiration to escape while not allowing water to penetrate. Each sock is high-pressure tested to make sure there are no leaks. Features: Windproof Waterproof Breathable Made in the USA Item Specifications: Mid-calf height (11") Inner: Merino Wool Outer: Acrylic/Elastane Available in Black Sizes: Small Women"s Shoe Size 6-7 Small Men"s Shoe 5-6 Medium Women"s Shoe Size 8-10 Medium Men"s Shoe 7-9 Large Men"s Shoe 10-11 Large Women"s Shoe 11 And Up X-Large Men"s Shoe 12-13