The RW-9 Compression sock is the only FIA approved compression sock on the market. It uses a seamless construction that delivers Class 1 compression force. This graduate compression force uses the same principles used in action sports. The RW-9 sock exerts maximum pressure at the ankle and then decreases going upwards towards the calf, to facilitate the upward return of blood circulation. This compression force is proven to minimize muscle fatigue to improve driver comfort and focus.FIA 8856-2000 homologated.