Quicksilver 55989Q9 Aluminum Anodes - MerCruiser Transom Plate Nuts Each anode Comes with attaching hardware for quick and easy replacement with common tools Produced to Meet Mercury marine original equipment Manufacturer specifications to best protect your mercuries drives and engine Inspect anodes periodically for best protection and replace when seeing signs of corrosion or pitting to help keep your maintenance costs down Don't let corrosion damage your mercuries stern drive or engine and reduce your boating pleasure Mercuries cast aluminum anodes meet or exceed mil-spec MIL-A-24779(SH) providing longer lasting protection than zinc anodes and are for us in fresh or salt water