With the addition of Merino Wool and earth tone colors, this lightweight running sock fits like nothing else out there. Patented SynchroKnit contruction drops stitches out of the knitting process to create a sock shaped like a foot, not a tube. This allows for proper support and a contoured fit.SynchroKnit patented contour knit, no unneeded fabricDouble Y heel gore provides most precise fit availableY gore toe box provides room for natural expansionSeamless internal toe seamSize and Made in USA sewn into cuff51% Merino Wool, 37% Stretch Nylon, 7% Polyester, 5% Spandex