For freshwater only Complete six-piece magnesium anode kit with fasteners for quick and easy replacement Produced to meet OEM specifications Mercury Marine for optimal protection of your MerCruiser Alpha One Gen II drive and engine in fresh water Prevent corrosion from damaging your MerCruiser Z drive or engine Inspect the anodes regularly for optimal protection Cast from high quality magnesium to fit perfectly on your 1991 and newer (serial number 0D469829 and up) MerCruiser Alpha One Gen II Stern Drive