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.