If you're going to choose fins, there's many types of fins, whether it's for your classic long board fin, you have a long base, which is giving you a lot of drive, and then you have a lot of area in this fin. So it's holding the board into the face of the wave.
This is your high performance long board fin. Now, basically, you can see the different style of fins. One is taller and skinnier with more rake. What the rake is, it's giving you projection. In other words, you can see with these two fins that this one has much more rake. What the rake does is give you drive down the line. It's projecting you down the line of the wave.
Whereas this fin has less rake, so it's more of a pivot fin. It wants to go up into the face of the wave. So all depending on how wide your base is and how much your rake is, that's what's going to determine the performance of your fin.
Now your fins, when the water flow goes around the fin, this is a double-foiled fin. It's curved on both sides meeting fifty-fifty in the center, and so the water flow is going around it, holding it down into the face of the wave, and then releasing off of the trailing edge.
Now with your basic thruster fin, the side with the curve goes on the outside, which is holding to the face of the wave, and the flat side, on the inside, is giving you lift and helping you hold into the face of the wave and giving you speed.
And you can see that with thruster fins, same thing. The different sizes of the base, and the different rakes in the angle of the fins, will give you different projections, whether you want to go down the line to pivot turns. It's all the different types. These are basically the types of fins you will get with your stock boards, and then you can upgrade your fins.
Now, they make a high tech fin which is a fiberglass fin with honeycomb inside. What this does, the honeycomb makes it really light, so your board is really balanced. They cost a little bit more but they're worth the money. And that is your fins.