the present invention provides a process for fluid assisted injection molding comprising the step of providing an injection molding apparatus having a mold body that defines a mold cavity . the process further comprises the steps of supplying a quantity of fluent plastic to the mold cavity , followed by injecting a fluid into the mold cavity . the fluid forms an expanding fluid pocket in the mold cavity , driving plastic to the furthest recesses of the mold and ensuring a smooth surface finish of the final molded product . a reservoir is selectively connectable to a plastic injection runner , and can be opened to the runner to receive molten plastic ejected by the introduction of the fluid to the mold cavity . when the reservoir is thusly connected , the pressure of the fluid forces the plastic through a supply passage , in a direction substantially opposite to its initial injection direction .