When the anode is 70% eroded it needs to be replaced. Canada metal uses a special steel combination fastener that makes it possible to use their ball driver, a hex driver with a universal ball tip, for easy adjustments. This is especially important to divers, who may have a difficult time with conventional fasteners underwater. Zinc is used for salt water. Not recommended for use in fresh water. Alloy is manufactured to meet or exceed US Military Specification (mil-a-18001k). Magnesium is used for just fresh water. Not recommended for use in salt or brackish water. The only alloy proven to protect your boat in fresh water! Aluminum is used for salt and brackish water. Not recommended for use in fresh water. Proven to last longer than zinc due to increased capacity. Alloy is manufactured to meet or exceed us military specification (mil-a-24779(sh)). Kit includes; 1 CM6G54525101A, 1 CM61A4537100A.

 PROP 65 WARNING: This product may contain chemicals known to the State of California to cause cancer and birth defects or other reproductive harm. Wash hands after handling. For more information, visit www.P65Warnings.ca.gov