FCS GX Glass Flex Surfboard Side Fins Can be used as longboard side bits or quad rears. Moulded composite fin with engineered flex and tip response. Small traditional longboard side bite designed to add speed, stability and control to any 2 + 1 set up.    Ideal Conditions A wide range of conditions from beach breaks to point breaks.   Board Types All board types. Will fit the FCS II Fin System when used with grub screws and the FCS Infill Kit. Glass Flex (GF) fins are molded from engineering grade polymer. The flex of these fins has been designed to help novice surfers maintain speed and acceleration as they learn to execute turns and maneuvers.