FCS UL-5 Tri Fin Set.From the UltraLight series of high tech fins, this medium size set features a top notch template made from the lightest possible materials. Carbon on the inside face gives a high tension “snap back” flex pattern through to the top of the fin without adding extra weight. The inner core ensures strength and foil accuracy without sacrificing flex. The result is a highly responsive, performance-driven fin that is very popular among the world’s best surfers. Optimum weight range for this size M tri set is: 143lbs - 176lbs (64.8kg - 79.8kg). FCS.