The Beuchat fin has a flexible vent system to help you power the so-called 'negative area' without having to make the blade stiffer.
A design of side rails has been used, causing a spring effect on the blades and also a 'scoop' effect at the tip of the blade, using very flexible materials.
The full foot pocket is close fitting with reinforced kick support in order to transfer the power from the foot straight to the blade. Side stiffeners in the foot cavities help powering the surface on longer fin strokes.
The fins have been kept lightweight with very efficient materials that Beuchat has extensive experience with.