Abstract: An apparatus for use in gas-assisted injection molding of plastic material so as to form an injection molded product includes a pair of mold members defining, when closed, a sealed cavity. A first opening is provided in one of the mold members for allowing the injection of a plastic material into the mold cavity and a second opening is provided in one of the mold members, and spaced from the first opening. A sleeve extends through the second opening. A probe extends through the sleeve and is adapted to be reciprocated therein from a retracted position to an extended position. The probe includes a first end adapted to selectively extend into the cavity, a second end and a longitudinally extending bore which terminates adjacent the second end. A reciprocating device is provided for reciprocating the probe in the sleeve held in the second opening of the one mold member in relation to the cavity.