Fins are your board’s steering and hold! The single fin of the longboard era gave way to the twin-fin for looser, skatey feel in the ’70s. Then came the thruster (three fins), invented by Simon Anderson, which gave insane drive and control, becoming the standard. Quads and even five-fins offer different combos of speed, pivot, and hold for specific waves. It’s all about dialing in your feel for different conditions, from small mush to pumping barrels.