New Futures Surf F4 Thruster Fin Set Pu Glass The F4 Techflex fin is one of our most popular models and a longtime favorite of John John's. The Techflex materials give this fin a responsive flex pattern, optimal for high-performance surfing in powerful waves. The F4 is one of the most balanced fin templates with a thicker tip that provides additional hold on rail. Techflex is stiff like Fiberglass, but lighter than Honeycomb The ultimate in flat foiled fins Great for powerful surfers or powerful surf Size: Small (105lb-155lb) (47kg-70kg)