There is provided a split mold insert and a mold stack incorporating same. The split mold insert for defining, at least partially, a neck area of a preform suitable for blow molding into a final-shaped article, in particular, is provided. The split mold insert comprises a body having (i) a cavity defining portion for defining, in use, a portion of the neck area and (ii) a top projecting portion and a bottom projecting portion located at opposite sides of the body; a first female taper portion associated with the top projecting portion; a second female taper portion associated with the bottom projecting portion; the first female taper portion and the second female taper portion for cooperating, in use, with a first male taper of a first mold component and a second male taper of a second mold component, respectively, for aligning the body into an operational configuration.