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$22.29PriceQuantity*Add to CartFeaturesID1-3/4"OD3-1/2"Length1-3/8"