this is a Pure High-Quality Magnesium anode rod made from top-quality magnesium AZ63-alloy for hot water heater RV water heater anode rods are made from superior quality, extra-durable magnesium guaranteed to withstand the test of time. Unlike classic aluminum zinc rods, our products are 100% safe for the entire family. These anode rods are 9.25” long, 3/4" NPT threads and are compatible with Suburban 232767 and Mor-Flo water tanks. How long does the anode rod need to be replaced? 1~2 years. It depends on the concentration of metal ions in water, the temperature, the contact area of water and exposed iron, the model of your water heater, and so on. Magnesium rods are more active than aluminum rods. It means that magnesium rods will be corroded faster but work & protect better. Package includes: 2 magnesium anode rods and 1 roll of PTFE tape.