A molding apparatus with which to mold, in use, a preform of the type for blow molding into a container, the molding apparatus comprising a lock ring (104, 204) for use in a first stack portion of a mold stack: the lock ring (104, 204) comprising a tubular body (150, 250) configured to define, in cooperation with a core insert and a split insert, a top portion of a molding cavity, a first aligning interface, a second aligning interface and a support interface, wherein, in use, with the core insert received within the tubular body (150, 250), the first aligning interface is provided between an inner conical face of the tubular body (150, 250) near an upper end thereof and an outer conical face of the core insert, and with engagement between the split insert and the lock ring, the second aligning interface is provided between a conical taper defined at the upper end of the tubular body (150, 250), and a complementary conical taper defined in a bottom portion of the split insert, and the support interface is provided between a support shelf (154, 254) and a bottom face of the split insert, characterized in that the support shelf (154, 254) is provided by a support flange (151, 252) defined by the tubular body (150, 250) near the upper end thereof, wherein portions of the support flange (151, 252) provide a first major promontory, a second major promontory and a pair of minor promontories being relatively narrow in contrast to the first and second major promontories (152, 153), the first major promontory and the second major promontory are provided on diametrically opposed parts of the support flange (151, 252), and the pair of minor promontories join ends of the first major promontory with ends of the second major promontory, and the support flange (151, 252) is such configured that the outer faces of the first and second major promontories (152, 153) have a substantially rounded shape, thereby providing an oval shape of the support flange (151, 252). the lock ring (104, 204) comprising a tubular body (150, 250) configured to define, in cooperation with a core insert and a split insert, a top portion of a molding cavity, a first aligning interface, a second aligning interface and a support interface, wherein, in use, with the core insert received within the tubular body (150, 250), the first aligning interface is provided between an inner conical face of the tubular body (150, 250) near an upper end thereof and an outer conical face of the core insert, and with engagement between the split insert and the lock ring, the second aligning interface is provided between a conical taper defined at the upper end of the tubular body (150, 250), and a complementary conical taper defined in a bottom portion of the split insert, and the support interface is provided between a support shelf (154, 254) and a bottom face of the split insert, characterized in that the support shelf (154, 254) is provided by a support flange (151, 252) defined by the tubular body (150, 250) near the upper end thereof, wherein portions of the support flange (151, 252) provide a first major promontory, a second major promontory and a pair of minor promontories being relatively narrow in contrast to the first and second major promontories (152, 153), the first major promontory and the second major promontory are provided on diametrically opposed parts of the support flange (151, 252), and the pair of minor promontories join ends of the first major promontory with ends of the second major promontory, and the support flange (151, 252) is such configured that the outer faces of the first and second major promontories (152, 153) have a substantially rounded shape, thereby providing an oval shape of the support flange (151, 252).