The Universal Bungee Strap is adjustable, one-size fits all, and fits on most open heel fins on the market. Its comfort-flex hinge, and rubber heel cup with a finger loop make for an easy fit. Adjustable bungee strap. One size fits all with five (5) adjustable positions. Will fit on most open heel fins available on the marker. Rubber heel cup with finger loop for easy fit. Bungee Strap. Anatomic Fin Strap.