Over 5 years of research and development brought the highly regarded and best- selling SF-8 X-Pert Zoom split fin to market in 2003. TUSA redefines the fin market again with the introduction of the SF-15 X-Pert Zoom Z3. The SF-15 further improves upon the performance, features and design of the SF-8 with the incorporation of 3 materials, 10% longer blade length, enhanced propeller- fin technology, reinforced blade rails and optimized blade scoops. These new features along with TUSA's patented 27 Angled Blade Design and EZ strap buckle system make the SF-15 THE fin for divers. TUSA's Angled Blade Design:When using the standard traditional blade fin, with the leg completely extended, there remains an angle of 27 between the heel and the foot and the calf of the leg, causing a 10% loss of propulsion. Because the fin is angled below the body, during the kick phase, the body is pushed forward and down, instead of straight ahead. With the SF-15 fin, that 27 angle has been designed into the fin. This means that 100% of the energy expended during the kick phase is directed toward the propulsion of the diver. To achieve maximum performance from this fin, use a small bent-knee kick with a light rhythm. This creates less strain on the leg muscles compared with traditional fins, reducing the diver's fatigue and subsequent air consumption.