The Kenetrek Montana Sock is a combination of low-micron merino wool and polypro fibers, giving you an incredibly strong yarn that allows a middleweight to act like a heavyweight in both warm and cold climates. They are strong, breathable, wicking, quick drying, odor and blister resistant, and immediately recover in the wash. Boot height, medium weight. Made in USA. 33% Merino Wool, 33% Polypropylene, 26% Nylon, 5% Elastic, 3% Lycra.