The M Series shortboard fins by FCS are designed to be fast and smooth with better hold and more squirt through turns. The new inside foil technology offers superior drive and the flexible tip provides forgiveness and control at high speeds.The Glass Flex material combines the flex pattern of a hand-foiled fiberglass finwith the ability to mold highly technical, computer generated foils accurately. Comes with three fins and a fin key. 4.37" base and 4.55" depth.