Sierra 18-6243 Mercruiser Alpha Magnesium Anode For use on RMRAlpha One Sterndrive Transom Assembly 1983-90Drives. Fits over trim line manifold. For fresh water use only. Material Magnesium Interchangeable with Mercruiser Stern Drive 97-821631Q1 97-821631C 821631A1 43994A2 821631B1 California Residents WARNING Cancer and Reproductive Harm - P65Warnings.ca.gov Other Details Google Product Type Engine Parts Wiser Yes Product MPN 18-6243 Product UPC 808282103613 Fast Ship In Stock Ships Today Deal