Martyr magnesium anode kit is designed to protect gearcase from corrosion in fresh water lakes and rivers. MerCruiser Magnesium Trim Tab Anode Kit | Martyr CM762145KITM Mercruiser trim tab anode kit Includes fastening hardware Magnesium anode for use in fresh water applications For Alpha I Gen II For Bravo I, II and III Use magnesium anodes in fresh water applications Magnesium aftermarket direct replacement for Mercury 97-76214A6 For Aluminum see p/n CM762145KITA