Anode Rod for Water Heaters
Suburban makes an aluminum and a magnesium anode rod. Every Suburban water heater comes equipped with a magnesium anode rod out of the factory. However, aluminum anode rods are available as a replacement as well.
The magnesium anode rod will work in any Suburban water heater, but they also make an aluminum one for areas with "harder" water.
It is suggested that you use the aluminum anode rod if you are west of the Mississippi river, and a magnesium anode rod if you are east of it. This is due to the hardness of the water.