A mould system for manufacturing a container which includes a movable mould half and a stationary mould half which are positioned opposite to each other, wherein the movable mould half includes a core plate provided with a core, a plate-like seal ring that is movable relative to the core, a seal surface which surrounds the core, and a collar ring that is movable relative to the core and the stationary mould half includes a mould plate provided with a mould cavity and a seal surface, wherein in the mould system, a plate-like insert is connected to the seal surface of the seal ring, the insert including a recess which is in contact with a front edge of the seal surface, so that it is in flow communication with molten plastic material flowing from the direction of the collar ring.