a method is disclosed for sealing or closing off the open end of a multilayered tubular structure , especially one having a barrier or low - gas permeable layer , whereby the integrity of said barrier layer is maintained . the method gives rise to a multilayered parison structure which comprises a cylindrical body having a body wall , an open portion terminating at one end thereof and a bottom wall at the opposite end of said body , said body and bottom walls being composed of a plurality of layers bonded together , all the layers of said bottom wall extending fully inwardly in contacting and overlapping relationship with like layers along the longitudinal axis of said cylindrical body , and a balancing member attached to said bottom wall , said member being composed of a single layer material forced therefrom while in a plastic state .