Finis - Edge FinsThe Edge fins are designed to improve technique and give your legs a real workout. It takes power to push these fins through the water, which results in building strength and endurance. The side rails on the fin activate your hips and quadriceps enforcing a proper kick that starts at your hips and not your knees. This motion is great for glute and hamstring development. Made of 100% silicone, Edge fins will mold to your feet over time, like breaking