The Spring Revolution 2.0 Winter Warm Evolution 921 Socks are Mid Size socks suitable for use in harsh climates. Made with Merino Wool, Prolen, Cutec and Emana, a mix of high thermal performance yarns that protect the foot from the cold even when the outside temperature is below thermal zero.Spring Revolution 2.0 Winter Warm Evolution 921 Socks FeaturesReinforced toe and heelFriction-free sewingSpring Revolution 2.0 Winter Warm Evolution 921 Socks Materials27% WO MERYNOS WOOL /26% PP PROLEN /20% PA POLYAMIDE COPPER CUTEC /17% PA NYLON F.I.R. EMANA /9% PA NYLON /1% EA LYCRASpring Revolution 2.0 Winter Warm Evolution 921 Socks SizingSmall (EU 35-38 / UK 3-5.5)Medium (EU 39-42 / UK 6-8)Large (EU 43-46 / UK 9-11)Approximate Sizing. More info