Home Fins Technology Contact About Lessacher Hyper Duo Speedfin Double Concave Asymmetrical Windsurfing Fin 100% Carbon Fin sizes (cm): 24 27 30 34 Sail size (m2): 5.5 6.5 7.0 8.0 The Hyper speed fins have an asymmetrical foil shape, where the concave transfer diagonally from one side to the other and thus prevents spin out on both tacks. The additional cut out at the base makes it possible to use larger sails. To compensate for a difference in how the foil works close to the surface vs. deeper, the concave surfaces are of slightly different size. This makes the fin work equally on both tacks. The concave near the surface is about 10% larger than the concave near the tip of the fin.