Thorlos TRMX Trail Running Ankle Sock 61% Thor-Wick COOL polyester, 18% Thor-Lon Acrylic, 17% Nylon, 4% Elastic Turn Inside Out-Machine Wash-Use Liquid Fabric Softner Fiber Contents: 61% THOR-WICK COOL polyester, 19% THOR-LON Acrylic, 17% Nylon, 4% Elastic Thorlo padding is clinically shown to reduce pain, pressure, blisters, and moisture Padding in the ball and heel specifically engineered for trail running Lightweight cushioning in the instep and arch for a better fit Low profile toe seem will not rub or irritate feet.