The Smartwool PhD Outdoor Ultra Light Mini Sock is a short sock with full foot comfort. Whether you're running or hiking, this sock will keep feet happy when spending time outdoors. The Merino wool, nylon and elastane blend Uses Indestructawool; Technology for durability and comfort. The ultra light cushion throughout cuts down on bulk and the 4 Degree; Elite Fit System dials in the Fit to prevent it from moving around. Features of the Smartwool PhD Outdoor Ultra Light Mini Sock Indestructawool Technology for enhanced durability 4 Degree elite Fit system for a dialed, Performance-oriented Fit Shred Shield Technology reduces wear from toes Body mapped mesh zones for added breathability Virtually Seamless toe for enhanced comfort Fabric Details 48% Merino Wool, 48% Nylon, 4% Elastane