BASE: The length between the leading and trailing edge where the fin meets the board. Base is primarily linked to drive. Fins with a longer base will offer substantially more drive and acceleration.


DEPTH: The distance the fin penetrates into the water. Depth directly relates to hold. The greater the depth the more hold, the shorter the depth the more a board will slide and release.


SWEEP: The angle measuring how far the outline of the fin is curved backwards; also referred to as rake. Sweep has a direct influence on pivot. Fins with more sweep produce a longer turning arc, less sweep offers a tighter turning arc.


FLEX: The distortion of the fin from its original shape caused by lateral pressure during a manoeuvre. Flex influences the response characteristics of a fin. Fins with little flex (stiff) produce instant response, speed and drive. Fins with more flex (flexy) are more forgiving and offer a whipping sensation.


CANT: The angle of the side fins measured from a vertical line perpendicular to the flat bottom surface of the board. Cant has a direct effect on acceleration and manoeuvrability. Less cant produces faster acceleration and a stiffer feel. More cant will increase manoeuvrability and gives the board a loose feel.


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.