Zinc: For use in salt waterAluminum: For use in brackish waterMagnesium: For use in fresh waterHULL ANODES (MARTYR ANODES)SKU: 6.28309E+11$29.29PriceQuantity*Add to CartFeaturesSize9-1/4" L x 3-3/8" W x 3/4" HHoleN/AMaterialAluminum