Fins are like the steering and accelerator of your board, dude. A single fin offers smooth, drawn-out turns. Thrusters (three fins) are the all-round standard, giving you great drive and control. Quads (four fins) are fast and loose, perfect for generating speed in weaker waves. It’s all about feel and what kind of waves you’re surfing. Swapping fins is the cheapest way to totally change how your board rides, so experiment and find what works for you.