Home Fins Technology Contact About Project Eleven Wave Duo Cut Double Concave Asymmetrical Windsurfing Fin Fin sizes (cm): 19 21 23 25 Sail size (m2): 5.5 6.0 6.5 7.0 These fins are made from two-colored G10 material and can be provided on order for any box type. The asymmetrical foil shape features a concave section near the fin base on one side and near the tip on the other side. The concave transfer diagonally from one side to the other and prevents spin out on both tacks. When landing small jumps in chop or waves, air is drawn under the board and onto the fin. The cut out at the base of the fin prevents the air pocket from attaching to the fin and allows it to be ejected behind the board.