Finis Edge Fins Check the size chart before purchasing, if you are between sizes or have a wide foot, we recommend sizing up. Designed to be worn during aerobic and anaerobic training to increase your endurance and speed. These will make your legs work hard! Side rails activate your hips and quadriceps  enforcing a proper kick that starts at your hips and not your knees. Constructed from a flexible, durable silicone  starts conforming to your feet after a few wears. Designed to catch water on the up-kick, activating hamstrings and glutes.