The first fin in the world made by combining three different materials, a process that Cressi perfected and patented with this fin, which guarantees unsurpassable performance. The blade is made from a special, incredibly reactive polypropylene, which is at the same time extremely light, and progressively charges up during the stride to take off like a spring at the exact moment the stride is inverted. A soft elastomer anatomically wraps around the foot, blocking it with a comfortable bite, which guarantees perfect transmission of the leg-fin thrust. A suitably solid copolymer hardens some critical zones of the foot, and is extended along the sides in two lateral stringers, which go halfway along the blade. The function of these stringers, assisted by special raised bands on the bottom of the blade, is to regulate and harmonise the bending, at the same time protecting it from shocks and abrasions. The fins are extraordinarily light compared to equivalent models of rubber footed fins and reduces the inertial masses to the minimum, to the full advantage of the effort-efficiency ratio. This fin is designed for deep skin-diving, although some Scuba professionals and instructors appreciate it a great deal.