This sock has a great foot fit design with integrated arch support, terry loop cushioning through the footbed, flat toe seam, breathing toe box, ultra re-inforced on the heel and ball of the foot. It is insulating, soft and durable, wicking moisture away like nothing you’ve ever experienced. They are a little heavier and more cushioning than you would expect but truly maintain your body temp without trapping excess heat. Designed for a dry cool comfort in hot environments, with superior moisture regain properties, and exceptional air-flow almost double the wicking of fine wool. Base Yarn Composition: 33% American bison down / 33% Merino wool / 33% Bamboo, Made in the USA. Sizes from small – extra large.