6 in. x 4 in. Mini Divers Dream Magnesium Hull Anode | Canada Metals CMDIVERMINIM Magnesium Martyr anode protects boat hulls from corrosion in fresh water lakes and rivers. Mini Divers Dream sacrificial anode Magnesium anode is for use in fresh water applications 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 5.9 in. length 3.9 in. height 1/2 in. thickness