Regrettably not SFI rated but could add +5hp (human powers) to your daily walk, gain .01g of lateral cornering force over stock socks. Made of 80% Cotton for softness and 18% Nylon / 2% Spandex for elastic durability. Crew length (i.e. over the ankle, below mid calf).
One size, fits men's 7 to 12.5 shoe size or women's size 8.5 and up. Wash in luke warm/cold water and low heat tumble dry. Some shrinkage out of the dryer can be expected but they'll stretch right back when you put 'em on. Lightweight to reduce unsprung mass. All socks are directional, symmetrical. We recommend rotating after ever wash cycle, or 3,000 walking yards, whichever comes first.