Developed by Sean Mattison for Von Sol surfboards, the FCS VS 'KNUBSTER' is a centre 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. It's designed with a single tab for the ability to move it forward and back based on drive.

The FCS VS KNUBSTER, which is 3 3/4" by 2" high, was the 5th fin Kelly Slater used on his quad during the Quiksilver Pro in New York. According to Kelly's report, "The KNUBSTER will make your quad set-up feel faster, smoother, and it adds a little more control".