This is the Oceanic Manta Ray Open Heel Scuba Diving Fins with Spring Straps Features: Techno-Polymer Blade - Advanced materials provides the strength of bone to maximize power, speed & efficiency, while being extremely lightweight & durable. Power-X System - This revolutionary material acts as tendon & joint, optimizing propulsion by flexing during the downstroke and releasing stored energy prior to the upstroke. Power Channel - The flexible center channel simulates the elasticity of skin by directing water flow off the back of the blade for increased thrust. Soft-Pad Heel Strap - Our newly designed heel strap has a comfortable and ergonomic finger-loop which allows the fin to be easily removed & replaced, even with thick neoprene gloves. Easy Buckle Adjustment (EBA) - Our unique EBA buckle adjustment system allows for more than 2 (5 cm) of precise adjustments for a custom fit without tools. Winglets - These have been positioned along the length of the blade to increase efficiency and improve maneuverability. The revolutionary design of the Oceanic Manta Ray fin was inspired directly from the shape and bio-mechanics of marine animals. By combining three different materials to simulate bone, tendon and fin, we've created a blade design that provides maximum power, speed & efficiency while also remaining extremely lightweight & durable. Of course, it's not all nature's technology, we added some of our own as well. Our new soft-pad heel spring strap has a unique ergonomic finger-loop that makes getting these fins on or off in any situation a snap. We've also replaced the standard buckle attachment points with our new Easy Buckle Adjustment (EBA) system. The EBA system allows precise adjustments for a custom and comfortable fit at anytime and without tools. This unique and unparalleled combination of materials and technology will deliver performance where ever and whenever you need it; from demanding currents and rough surf to long surface swims, the Manta Ray will get you there. "