MKP-30 Part# 2198400 Replacement anode kit for 3-1/4" and 3-5/8" motors. Balanced-design anode attaches quickly and easily to prop hub. Eliminates corrosion of other metallic components. A key component in the engineered-superiority of Riptide motors. MKP-30 fits 3-1/4" and 3-5/8" diameter lower units.(this anode) MKP-31 fits 4" and E-Drive diameter lower units.