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$19.39PriceQuantity*Add to CartFeaturesID1-3/8"OD3"Length1-1/4"