Ultra Lightweight - Our lightest sock for race day or anyone looking for a lighter-than-air feel from a tougher than hell sock. True Seamless technology allows for an undetectable seam fusion for an ultra-smooth, invisible feel. Over-The-Calf Height - The name says it all. The ultimate height for keeping the outside-out. Composition - Knit with 55% Nylon 42% Merino Wool 3% Lycra Spandex. The fast action wicking pulls moisture away from skin, so no more sweaty, stinky socks. The soft, breathable merino wool has fast drying, all weather performance that keeps you cool in the summer and warm in the winter. Guaranteed for Life - If these socks wear, tear, or develop holes, Darn Tough will replace them. No strings. No conditions. Made in the USA - Every pair of socks is knit in Vermont - the perfect testing ground for the finest premium all weather performance socks.