Oceanic USA Warrior Line Vortex V-16 Split Open Heel Fins with Spring Strap for Scuba Diving or Snorkeling (SM) Patented Nature's Wing Propeller Fin Technology with four (4) material compounds for ultimate performance and light weight Semi-rigid battens and natural rubber flex channels precisely control the shape of the blade during the fin stroke to optimize power and reduce drag Oversized side rails add rigidity and control movement of the blades for increased lift, power and efficiency Ergonomically designed foot pocket accommodates virtually all foot sizes and boot styles Angled blade for preferred angle of attack