This demonstration video discusses and shows the features of the Hollis F1 "Bat Fin" Adjustable Spring Strap Dive Fins. It comes with free Depth Compensating Steel Spring Straps. The fins are made out of a high grade heavy-duty bulletproof rubber construction. The Hollis F1 "Bat Fin" has angled strap mounts for comfort and a better transition of power with Easy-grip on/off fin strap thumb loop and multiple strap mounting positions for a fine tuned fit. The fins feature a vented blade to reduce stress while accelerating water over the blade and have a generous foot pocket.