A quad setup has four fins on the bottom of the board. This setup generates a lot of speed, because there is no drag caused by a middle fin. However, the lack of a middle fin decreases the control of the board. Though, in large, steep waves, a quad setup allows for a more targeted control, without decreasing the speed. During smaller surf conditions a quad setup makes it easy to create speed. In general, this setup is perfect for generating drive while making turns! The quad fin sets consist of four fins: two side fins and two rear fins. Check out, for example, the quad fin sets of FCS, Future fins and Captain Fin!
Check out the Ultimate Surfboard Fin Guide for more information!