The Rheem SP11526C is a magnesium anode rod. R-Tech Resistor, 44 in. x 0.9 in. diameter. Anodic Material: Magnesium. Total Length (in.): 44-3/8 in. Rod Diameter (in.): 0.9 in. Hex Head Size (in.): 1-1/16. Thread Size - NPT (in.): 3/4. Resistored: Yes.