FCS Q-5XC Glass Flex Surfboard Quad Fin Set (M5 With GX Centers) - Clear The Q 5XS fins are suited to longer boards and funboards in most conditions, or short boards for very small surf Fast and smooth, with better hold and more squirt through turns The M-series has a flexible tip for forgiveness and control at high speed The new inside Foil Technology offers superior drive and hold Advantages over other composite fin materials inlcude stiffness, a more positive flex pattern