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)