Electric 300 Series Mobile Elevated Work Platform (MEWP) Slave Cylinder (Platform Level Cylinder) Assembly. The Slave Cylinder is located at the end of the main boom assembly, to control the operator's platform level as it travels up and down. The cylinder is connected to the main boom on the barrel end and either JIB or Rotator/Actuator connection at rod end. The cylinder is compatible with JLG model(s): E300AJ, E300AJP. Ensure proper assembly and serial range of machine.