The Base measures what is usually the widest point of the fin’s outline. The base length impacts the way that a board will turn and drive (accelerate through turns).
A longer base provides more surface area to push against the water, so turns are stronger and drive is increased. However, the larger base doesn’t permit the board to turn sharply, so if that’s what you’re after, go for a fin with a shorter base length.
The depth of a fin is basically how far it sticks into the water, measured from the bottom of the surfboard to the tallest point on the fin.
Depth affects the way a board will grip the water through turns, and it determines how well the board remains stable. The taller the fin, the more hold it will have in the water, providing the rider more control. While shorter fins don’t grip the water as well, they do allow the board to slide-out a little, which some surfers enjoy.
The Area of a fin measures the running surface of the fin where it makes contact with the water.
The term "Foil" refers to the shape and geometry of the inside and outside faces of the fin. Foils directly affect the flow of water over the surface of the fin. Different foils create variations in water flow and have a direct link to the overall performance of the fin and the board.
Surfers come in all shapes and sizes, this weight range is a suggestion to help you find the fins that fit you best. That said, this guide should be looked at as a guide and not a rule. Some larger surfers like smaller, looser fins and some smaller surfers like the stability provided by larger fins.
Size Extra Small (XS): Surfers under 130 lbs
Size Small (S): Surfers from 110 lbs to 160 lbs
Size Medium (M): Surfers from 135 lbs to 180 lbs
Size Large (L): Surfers from 155 lbs to 210 lbs
Size Extra Large (XL): Surfers over 185 lbs
Single Tab System - These fins are compatible with surfboards utilizing Futures Fins or Channel Islands single tab fin boxes.