The Power Blade, another original George Greenough design, was created with the intention of pushing the boundaries of the modern-day single fin surfboard. Through meticulous material selection, endless hours of testing, design revisions, and a uniquely constructed flex pattern, the Power Blade now has the potential of rivaling the performance characteristics of the thruster.
Here, Marc Andreini summarizes the Power Blade's function... "Although the thruster took surfing to a higher performance level (following single fins) with more speed and quicker responsiveness, we lost a lot of flow, trim, deep bottom turning and down the line style that went with single fin style surfing.  Now we can take that style, and up the performance to match the speed and virility of the postmodern board without sacrificing the flow."
The most important design aspect of the Power Blade lies within its ability to flex and ‘twist-off’ at the ‘head’ of the fin. This attribute provides variable-tow, similar to how a thruster works, which allows the tail of the board to follow the nose and in turn produces drive. In some ways it acts like a fish tail, flexing and twisting back and forth creating propulsion based on direction and angle of attack. The narrow base permits for an extremely minimal amount of water pressure resistance, allowing for a significant amount of response, speed, and maneuverability within a single fin.    
The main challenge in successfully producing this design, came through the need to retain a very stiff and extremely strong ‘leg’ in order to support all the load on the 'head.' Through extensive research and testing we finally landed on an extremely unique lay-up combination of high-density epoxy and fiberglass materials that met the qualifications without suffering fatigue. Our Power Blade fins meet 3 different demanding requirements within a singular fin… stiffness where needed, flex, and the ability to twist.
Find more information from Andreini here regarding performance characteristics of the Power Blade.