A blow head mechanism for an I.S. machine wherein the blow head has a final blow tube. The final blow tube is supported for vertical displacement between an up position where the open end of the final blow tube is proximate the top of a blown parison and a down position where the open end of the final blow tube is proximate the bottom of a blown parison. The final blow tube is oscillated a plurality of times during the time when the blow head is “on”.