Abstract: The present invention provides an injection mold apparatus for plastic piece molding. The apparatus includes male and female body parts and a gas blow-off ejection system for ejecting pieces formed on the male body part. The blow-off system includes side and top opening vents in the male body part for initial release and slight lifting of the piece and a further bottom positioned final blow-off vent, which is covered by slideable means during introduction of the plastic to the mold to prevent the plastic from flowing into the final blow-off vent and which is only exposed when required for completing blowing of the piece from the male body part. The slideable means has a slide tolerance to substantially eliminate flowing of the mold material therearound while being readily slideable when required for exposure of the blow-off vent to the male body part.