Zinc: For use in salt waterAluminum: For use in brackish waterMagnesium: For use in fresh waterHULL ANODES (MARTYR ANODES)SKU: 6.28309E+11$13.29PriceQuantity*Add to CartFeaturesSize4-3/4" L x 2" W x 3/4" HHole1-1/4"MaterialAluminum