Zinc: For use in salt waterAluminum: For use in brackish waterMagnesium: For use in fresh waterHULL ANODES (MARTYR ANODES)SKU: 6.28309E+11$26.79PriceQuantity*Add to CartFeaturesSize7-1/2" L x 2-3/4" W x 1/2" HHole1-3/8"MaterialZinc