A container strip in the form of a chain of interconnected preopened bags with openings having longitudinal dimensions of at least about 1/32 inch is disclosed. The container strip provides greatly enhanced facility for bag registration and opening during packaging operations utilizing the improved container strip. A process of forming a chain of pre-opened bags is also disclosed. Face and back plastic webs are independently fed along individual paths of travel to a common path. The webs are differentially tensioned while in their independent paths by stretching the face web more than the back web such that the face web will retract longitudinally more than the back web upon release of the web tension. While so tensioned edge seals are formed between the webs to convert the webs into a tube and longitudinally spaced transverse seals are formed between the webs to delineate bottoms of bags. Transverse lines of weakness are formed in said back web to facilitate separation of bags from the remainder of the web during a subsequent use. Tension in individual bag sections of the face web is released by forming longitudinally spaced transverse separations of the sections and thereby producing a space between each contiguous pair of sections.