The Sierra 18-6241 Anode is composed of high-quality magnesium. Designed to be interchangeable with the following: Honda 41107-ZW1-003ZA, Mercruiser 97-31640Q4, 316404, 31640, 31640A1, Mercury 31640, 97-31640Q4, 316404, 316403, 31640A2, 31640A4, 31640B4, 72436A1. Each Sierra product meets or exceeds the original equipment part it replaces.