1-23/64IN FRIGOBOAT ZINC ANODE FRIGOBOAT ZINC ANODE Our zinc and aluminum sacrificial anodes are manufactured in the US to ensure the highest quality of corrosion protection.They are manufactured for use on Recreational, Commercial and Military vessels, placed on hulls, propeller shafts, rudders, trim tabs, outboard engines, stern drives, and in the cooling system of most inboard engines to protect metal parts from galvanic corrosion. Material: Zinc Alloy- For use in Salt Water;- NOT recommended for use in Fresh Water;- Alloy is manufactured to meet or exceed U.S. Military Specification (US Mil-A-18001) Don t be fooled by claims that only one alloy will protect in all water environments. AttributesHole17/64"Size1-23/64" dia. x 9/32" T For Frigoboats "Keel Cooler" marine refrigeration system. Sold Individually. Two anodes required.