The Smartwool PhD Run Ultra Light Micro Sock is a durable running sock with minimal cushioning and no show style. Indesructawool; construction Features fine merino wool that's reinforced with nylon mesh and a bit of stretch for enhanced durability and comfort. Stride at your own pace over long distances or short jaunts, whatever you're up to these lightweight socks will keep your feet cool and dry for the duration. Features of the Smartwool PhD Run Ultra Light Micro Sock Indestructawool Technology Features a wool-based, patent-pending yarn and construction method for exceptional durability and comfort 4 Degree elite Fit system Uses two elastics for greater stretch and recovery. Run-specific Fit Mesh ventilation zones designed specifically for male runners provide optimum temperature regulation and moisture management Virtually Seamless toe Achilles tab Made in USA