Fitness Fins are designed to enhance your body’s natural ability in the water. Their dual density design – a stiff blade with a soft, comfortable foot pocket – is tailored to improve your performance and speed during your swim workout. Through increased resistance comes a bigger muscle workload, strengthening your legs and building endurance. Fitness Fins also force ankle extension during kicking, which makes the kick more propulsive and efficient. Biofuse Speedos Biofuse offer optimum fit and comfort and are designed to enhance the body's natural mobility and strength in the water. These products represent a balance of strength and flexibility, just like the human body, which is the inspiration for Biofuse products. They work in harmony with the body.