Martyr Anodes are pressure die-cast and manufactured to strict quality standards through an ISO 9001 Quality Management System. In addition, each alloy is guaranteed to be manufactured to the latest US Military Alloy Specification and is chemically tested regularly in our in-house labs to ensure consistency. Copies of Material Certificate of Compliance are available upon request. Poorly manufactured anodes may contain high levels of impurities such as iron, which will leave your investment unprotected. Martyr anodes provide low cost cathodic protection of ocean-going vessels, structures and equipment constructed of iron, steel, aluminum, magnesium and other metals. Martyr is the only manufacturer that offers all three alloys for all water environments for pleasure craft and commercial vessels.For use in fresh waterThe only alloy proven to protect your boat in fresh waterRudder anodes are sold in pairs, with stainless steel bolt and nutEasy installation underwaterWeight: 0.03kg