This is a four season sock, great cushioning and support for standing in a river tossing flies at salmon, long hikes, hard hunts, and basically just keeping your feet dry and comfortable in most conditions. They will stay fresh and funk free for days on end… pack less, travel more. Less bulk and better fit, but built to take whatever you can throw at them and still keep you cozy. Base Yarn Composition: 33% Bison Down 33% Ultrafine Merino Wool 33% bamboo fiber, Made in the USA. Sizes from medium – extra large.