A mold split insert for use in a molding stack assembly, and in particular a preform mold neck ring insert for use in an injection molding stack assembly for making bottle mold preforms. The split insert comprises a body with a molding surface configured thereon. The split insert also includes a coolant channel configured in the body with a partition arranged therein. The partition dividing a portion of the coolant channel into a first and a second branch. A transfer coolant channel is configured between the branches.
