FCS FK-2 Performance Core Fish Keel Twin FinsMedium 2 tab fish keel designed for retro twin set ups. Overview Medium 2 tab fish keel with 80 20 foil has less area and more flex than a traditional keel. This keel will add a little more manoeuvrability and freedom to any retro twin set up. Twin setup (2 fins) included. Board Types Designed to fit the FCS Fin System. Recommended for all board types including fish, funboard and twin fin boards.