Developed by Sean Mattison for Von Sol surfboards, the FCS VS KNUBSTER is essentially a center fin that can be added to any quad set-up. The fin will increase drive and provide directional control through turns, without sacrificing speed, flow, or the freedom of movement typically associated with a quad.The "KNUBSTER" is designed with a single tab that allows the fin to be positioned in the forward and rear center plug to cater for the individual drive requirements of each surfer.The FCS VS KNUBSTER, is 3 3/4" by 2" high. According to Kelly Slater"s report, "The KNUBSTER makes your quad set-up feel faster, smoother, and it adds a little more control. It just tightens everything it up a bit".