The Estate Swing E-S 300 and E-S 500 use the same control board, have the same motor, and are similar in all other kit inclusion aspects. The only difference is the length of the motor piston. The E-S 300 has a 300mm stroke length and the E-S 500 has a 500mm stroke length. The stroke length is the distance the piston travels in and out. The longer the stroke length is the larger the gate the operator can handle.