The Volvo Penta Anode CM851983M is a specialized magnesium sacrificial anode designed specifically for the S. DRIVE 120 Series engines. As a magnesium component, it is engineered for use in freshwater environments, where its high driving voltage provides superior protection against galvanic corrosion compared to zinc or aluminum alternatives. This specific model (PID: CM851983M) is lightweight, weighing approximately 0.286 lbs (0.130 kg), and features precise dimensions—including an outer diameter of 96mm and a height of 27mm—to ensure a perfect fit for Volvo Penta sterndrive systems. By corroding in place of vital engine components, it helps maintain the structural integrity and longevity of the vessel's propulsion system.