Injection molding apparatus has upper and lower mold halves that split along the center line of the parison cavity and the gate passage leading thereto. Each hot melt injection nozzle is received within a tubular insert cup having a reduced diameter tip that is seated within the gate passage. The cup is supported on the lower mold half so as to remain thereon as the upper mold half opens and closes the mold. The base end of each nozzle has a swivel ball and socket relationship with the manifold block which supplies it with hot melt, while the tip end of each injection nozzle is configured to permit swivelling within the insert cup as need be to accommodate dimensional changes that arise during non-uniform thermal expansion and contraction of different parts of the tooling.