Martyr CM123009Z, Zinc Alloy Bombardier Johnson/Envinrude Small block Anode Provides low cost cathodic protection of ocean-going vessels, structures and equipment constructed of iron, steel, aluminum, magnesium, and other metals Zinc Alloy for use in saltwater Cathodic protection for Pleasure craft boats Not recommended for use in fresh water High-quality Martyr anodes are pressure diecast and manufactured to strict quality standards through an ISO 9001 Quality Management System Mil Spec Alloy Zinc Alloy for use in saltwater