Streamlined Bolt-On Zinc Hull Anode | Martyr CMMZC406 9 in. x 4.4 in. oval zinc Martyr anode protects boat's hull from corrosion in salt water. CMMZC406 sacrificial anode Zinc anode is for use in salt water Martyr anodes are made of a high purity specialized alloy based on the US Mil Spec Bolt-on style anode is designed to mount to hull 9 in. length 4.4 in. width 1 in. thickness 5 in. bolt hole center to bolt hole center Replaces Canada Metals Z406