Size L. Used once. ¥3,630 Reversible black and white fin socks. You can use them to match the color of your fin's foot pocket. These 1mm thick socks are the thinnest available, allowing you to transfer power from your feet to your fins effectively. Recommended for entering the water from boats or sandy beaches. * Product Name: 1mm Reversible Fin Socks * Brand: DoubleK