Material: Neo Glass Neo Glass fins are precision molded using long strand fiberglass and a marine grade polymer. Very affordable yet considered a premium construction due to its high fiberglass content and active flex pattern, these fins will accommodate a wide range of surfers and surfing conditions. Board Types Designed to fit the FCS II Fin System. Recommended for all board types including fish, funboard and twin fin boards. Size: X-Small: Under 55Kg / 120 Lbs Small: 55Kg - 70Kg / 120 - 155 Lbs Medium: 65Kg - 80Kg / 145 - 175 Lbs Large: 75Kg - 90Kg / 165 - 200 Lbs X-Large: Over 85Kg / 190 Lbs