Cadmium free, environmentally friendly.. Aluminum: For salt and brackish water. Conform to: Mil-Spec A-24779(SH). Magnesium: For freshwater only. Conform to: Mil-Spec A-21412(SH). Includes:. Block anode for lower unit (1). Bar anode for mounting bracket (1). Button anode for lower unit and engine cooler system (4)