Molds, mold assemblies and stack components

A preform cavity insert comprising a molding surface along its length, a substantially cylindrical body with flat sides to provide a substantially obround cross-section, a mounting face at or adjacent one of its ends for mounting the cavity insert to a cavity plate, and a spigot projecting from the mounting face for receipt within a seat of a cavity plate, wherein the spigot comprises a cooling channel inlet and a cooling channel outlet for fluid connection with respective cooling channel openings in the seat of the cavity plate, the cooling inlet being described by a first axial slot through the spigot, the cooling outlet being described by a second axial slot through the spigot, one or more cooling channels extending along and adjacent the molding surface, wherein the one or more cooling channels comprise a plurality of axial channels connected together by one or more transverse channels, and wherein the spigot further comprises a radial hole parallel to the flat sides of the body, the radial hole for receiving a retaining pin extending into a gate insert seat, wherein the radial hole and the cooling channel inlet and outlet are spaced equally about the periphery of the spigot such that the cooling channel inlet is on a first side of the spigot, the cooling channel outlet is on a second side thereof, opposite the first side and the axial hole is between the cooling channel inlet and outlet and orthogonal thereto.