Running Crew Sock - The "Original" Double Layer Anti-Blister System that Serious Runners Demand. Dri-Wright/MicroSafe Inner Layer. Dri-Wright Outer Layer. Flat Knit. "Thin Sock Won't Compromise Shoe Fit." Inner layer: 70% Dri-Wright polyester, 30% nylon Outer layer: 68% Dri-Wright polyester, 20% Nylon, 4% lycra |