Zinc: For use in salt waterAluminum: For use in brackish waterMagnesium: For use in fresh waterLIMITED CLEARANCE SHAFT ANODE - WITH ALLEN SCREW (MARTYR ANODES)SKU: 6.28309E+11$15.99PriceQuantity*Add to CartFeaturesID7/8"OD2-1/8"Length1"