Abstract: Bubble-type flexible cushioning and packaging sheets are formed using films which are composites of single extrusion or multiple extrusion polyethylene films having density, molecular weight and, optionally, additives selected to provide a desired combination of qualities including heat sealability and low gas/vapor transmission. A preferred film material has a cross-sectional profile consisting of an inner region of linear low density polyethylene material surrounded by outer regions of high molecular weight medium density polyethylene material. The material permits the formation of preferred, square bubble configurations using a process which involves sealing two such films along generally parallel longitudinal lines; inflating the films between the longitudinal sealing lines; then sealing the films along transverse lines to form inflated rectangular pockets or bubbles therebetween.