Preform and mold stack

A mold stack for injection molding a preform having a neck, a body and a base, the mold stack comprising:

• a core insert comprising a first cavity defining portion configured to define an inner face of the neck and the body of the preform and, via a gate defining portion thereof, an inner face of the base of the preform,
• a split mold insert pair configured to define an outer face of the neck of the preform,
• a cavity insert configured to define an outer face of the body of the preform, and
• a gate insert comprising a second cavity defining portion configured to define an outer face of the base of the preform;
• the gate defining portion of the first cavity defining portion of the core insert having a first elliptical curvature with a first flat circular bottom portion, and the second cavity defining portion of the gate insert having a second elliptical curvature with a second flat circular bottom portion, and
• the first and second flat circular bottom portions each having a center on a vertical center axis of the mold stack and a radius R of equal size.