Sierra 18-6011 Zinc Anode Sierra high-quality engine parts are designed to meet OEM specifications. Constructed of zinc. Fits most MercuryMariner OBs 35 HP above and all Mercruiser engines except Bravo Use with 18-6245 Anode Mounting Bolt Interchangeable with Honda Outboard 41107-ZW1-003ZA Mercruiser Stern Drive 97-31640Q4 316404 31640 31640A1 Mercury Marine 31640 97-31640Q4 31640A1 316404 316403 31640A2 31640A4 31640B4 72436A1 California Residents WARNING Cancer and Reproductive Harm - P65Warn