Abstract: The present invention relates to a sack made of thermoplastic film, said sack having front and rear panels and an open mouth top portion, gusseted side walls wherein the innermost reach of the gusset folds overlap and at the bottom of said sack a heat seal stripe welds together all of the lay-flat layers, including the overlapped regions.

Abstract: A sack of a thermoplastic film comprising an open mouth region, a body region and a closed bottom region, said body region having at least one cold-stretched, circumferential band of reduced diameter therein. The method of forming such a sack comprising providing a sack of thermoplastic film; folding said bag at least once longitudinally so that the fold line is at least generally at right angles to the bag mouth opening; and at ambient temperature, applying a stretching force within at least one comparatively narrow band region across the folded bag, said stretching force being sufficient to neck-down the plastic film to a reduced diameter in relation to the original diameter of said bag.