Gorilla Mens One Size Moon Beams Mellon Gorilla Grip Moon/Beams/Melon tri-quad medium FCS II fins. Medium tri-quad (5 fin) set with 1 moon, 2 melon, and 2 tie-dye fins. FCS II system. Designed with a flat foil on the side fins delivering fast, controlled directional changes. Fin size: Medium.