Filling imbalance in geometrically balanced feed systems of multi-cavity injection molds is observed in “H” runner layouts feeding eight or more cavities. It is known that the imbalance results from non-symmetrical temperature and shear rate distribution. In this paper, the filling imbalance, and balancing of the melt flow between cavities using several MeltFlipper overturn geometries have been studied experimentally for various materials of different thermal and rheological characteristics, as well as for various flow rates. The Moldflow Platics Insight software has been used for simulations. It has been concluded that filling imbalance, and MeltFlipper balancing is strongly dependent on the thermal and rheological characteristics of the material, the runner layout and runner geometry size, and the molding parameters, e.g. injection flow rates. Two factors influence the flow imbalance, the shear rate distribution, and conduction heat loss from the melt to the mold. When flow rate increases, the shear rate imbalance also increases, and this would explain the increasing flow imbalance with increasing injection flow rate. However, at slow rates there is more time for conductive heat loss from the melt to the mold, and this would explain the increasing flow imbalance with decreasing injection rate. It may be concluded that MeltFlipper device provides a useful solution to balance the filling between cavities. However, the proper design of the device depends on the material, runner system geometry, and process conditions. If the design parameters are inappropriate, the imbalance still happens. Hence, the assistance of the suitable CAE tool is desired, and one can handle this phenomenon effectively.