Darn Tough over-the-calf socks are terry rib knit for a custom fit. High density cushioning surrounds entire foot and lower leg. Custom shrink treated Merino wool. Ribbing above the ankle ensures a proper fit. Reinforced heel and toe. Elastic support around the arch. Ring toe construction for a comfortable, invisible seam. Generous sizing: calf stretches 1” more than our traditional sock fit, allowing for a wider range of fit. Machine Washable.