Aqua Lung Express SS FinsAlthough there are many great features to this fin, look at the armadillo hinge of grooved material on the top of the foot. This specialized feature absorbs energy from your kick and releases it again at the end of the kick cycle for a more efficient kick and reduced strain. Includes Spring Straps for easy on off. Features: Armadillo Power. Armadillo Hinge at the blade base absorbs energy on the downstroke and releases it on the upstroke, giving you a