Speedo Biofuse Fitness FinGet more from your training with the Biofuse Fitness Fin. Speedo's comfortable fitness fins feature stiff blades for maximum water resistance and a more challenging lower body workout. Providing extra propulsion to your stroke, they promote better ankle mobility and provide easy speed so you can focus on your body positioning or kick technique. 100% silicone for excellent comfort. Speedo Biofuse technology for maximum comfort and fit 100% Silicone for