Aqua Lung X Shot Spring Strap Diving Fin Quick release, quick-adjust buckle makes adjusting a snap New spring strap offers a soft TPR heel pad along with Aqua Lung&#39;s own proprietary buckles The blade contains a high performance elastomer resulting in high efficiency An elastic blade insert creates a spoon effect that pushes more water with each down stroke adding to efficiency A customized inner sole provides a grip effect. This prevents wasting power from the boot moving laterally inside