C4 MB Series Fin - for 250 Footpockets (sold separately)These MB fins are our best interpretation of the concept of traditional carbon fiber fins. For the development of these fins we started from the design of the foot pocket. MB Fins feature the new 250 foot pocket, a direct derivation of the previous 300 model. In MB fins, the major factor that increases performance is the new dedicated Reverse Parabolic lamination; a parabolic curvature which, instead of having the part with greater flexion at the top,