Abstract: The invention provides a linkage for transmitting axial reciprocating movement from one shaft to a parallel shaft and comprising a bar pivotally mounted at a fixed but adjustable position relative to the shafts, the bar being pivotally mounted at a fixed position on the bar, a pivotal connection fixed on one axial shaft and slidably mounted on the bar to one side of its fixed mounting, and a pivotal connection fixed on the other axial shaft and slidably mounted on the bar to the other side of its fixed mounting. The linkage may especially be used in the drive of the plunger of gob forming apparatus for use in the production of glassware whereby by adjustment of the linkage the plunger stroke and height may be varied.