The container is one of the main elements for the performance of the extrusion process. The container mantle has the function of supporting the liner in order to prevent a breakage of the liner under high extrusion pressures. The pressure needs to be distributed homogenously from the liner to the container. And this is possible with a proper shrink fitting process. Naturally will the shrink fitting constitute a pressure on the container due to the squeezing of the container by the shrink fitted mantle. Finally is this external pressure there in order to balance the generated pressure during the extrusion. The support needs to be continuous and homogenous distributed during the whole extrusion.

An interruption of this support can cause the exceeding of the plastic flexion limit of the container and a resulting deterioration of it.