Copper provides a lower coefficient of expansion, higher tensile strength, and ideal conductivity.  copper rotor construction gives you greater reliability, efficiency, and versatility with which aluminum cannot compare.

• Lower Coefficient of Expansion - Aluminum will creep and move approximately 33% more than copper. This large movement will eventually lead to fatigue failure in rotor material due to thermal expansion and contraction.
  
•  copper rotor design ensures higher reliability compared to aluminum bars.
• Tensile Strength - Copper is 300% stronger than aluminum and thus able to withstand high centrifugal force and repeated hammering of the current-induced forces during each start.
• Higher Melting Point - Copper can better withstand thermal cycling over the life of the motor.
• Conservative Temperature Rise - Copper features conservative temperature rise limitations which prevent excessive deterioration in mechanical properties.

So go ahead ask other seller see if there pump are copper rotor (if they sell lower than my price for this pump they are most likely to be aluminum)

• Power Voltage: 110V / 110v 60Hz / 370W / 3,400 RPM  (hot wire set up)
  

  1/2 HP Long Lasting Motor

  Suction Lift Up To 29 Ft. 9m Fluid Temperature Up To 140 Deg F. Maximum Ambient Temperature 104 Deg F.

• Qmax is 35 L/min or 9 Gallon per minutes   552 gallons per Hour

  1" Inlet And 1" Outlet Threaded