Martyr CM865182CA, Aluminum Alloy Bravo 3 Mercury Prop Nut Provides low cost cathodic protection of ocean-going vessels, structures and equipment constructed of iron, steel, aluminum, magnesium, and other metals Aluminum Alloy for use in salt & brackish (mixed) water Protects 50% longer than traditional zinc anodes Contains no Cadmium, making it environmentally friendly High-quality Martyr anodes are pressure diecast and manufactured to strict quality standards through an ISO 9001 Quality Management System