Lorpen Primaloft Midweight Hiker Socks 75% Primaloft yarn/ 15% Nylon/ 10% Lycra Imported PrimaLoft Yarn is comprised of 50% Merino Wool and 50% PrimaLoft Insulating Fibers to deliver extraordinary wicking and drying properties Instep cross brace. X marks the spot of our Lycra cross brace that hugs the sock to the top of your foot, ensuring a very sensitive area remains wrinkle free. 10% of the overall yarn content is knit with real Lycra yarn from Invista. Flat knit toe seam: its expensive to make toe seams with this special stitch, but we think it delivers a superior seam that is virtually impossible to feel.