The PGP sprinkler head has been around since the beginning of Hunter Industries, and has been the foundation of many sprinklers built since then. The PGJ was only recently introduced, because many contractors requested a rotor type head that would cover a smaller area. While flow rates may be similar, depending upon the nozzle used, the PGJ is designed with a smaller radius for small lawn areas, and the PGP is designed with a larger radius for large lawn areas.
Tony Posey
Ridge Run Landscapes