The Hiking Mid Knee Socks from SEALSKINZ are waterproof hiking socks at level 3/5 on the Sealskinz scale of thickness, making them very versatile. StretchDry technology makes the socks both stretchy and waterproof: Padded heel, sole and toe cap, Hand-tied toe closure provides extra flat seams, reducing the risk of chafing, 38% Merino wool, 38% Acrylic, 22% Polyester, 2% Elastane, S=36-38, M=39-42, L=43-46, XL=47-49.