Endorfins Slater KS1 FCS II Tri Surfboard Fins - FCS II - Small/GreenSlater KS1 small size tri fin surfboard FCS II fin set from Endorfins. Designed by 11 time world champion surfer Kelly Slater. A better build innovative carbon inlays in Endorfins add strength and flex that enable them to be built with a core comprised of 90% pure air. As a result, Endorfins not only provide optimum performance but also literally float on water. FIN BOXES: Each set is built with a base that is compatible with either TWO TAB FIN BOXES