Flexible packaging pouch is used widely for foods, drinks, drugs and other materials. Flexible packaging usually consists of multiple layers of plastic films of different kinds.

Printing is generally on the outermost layer. BOPP is known for its quality of printed images. The innermost layer often uses either CPP or PE that are heat sealable. The middle layer(s) use PA for its strength and heat resistance, PET for its moisture resistance, or other plastic films for their special properties. Aluminum foil (AL) or plastic film coated with metal (such as VMPET) may be used to significantly enhance the ability to prevent oxygen, moisture or light from entering the bag.

Most of plastic pouches are flat that are sealed at three sides of left, right and bottom (side sealing). The upper side is left open for packaging process. This type of pouches is flat (width=0). However, a pouch could be formed by sealing at back panel (back sealing). Folding the plastic film at left and right sides of a back-sealed bag could leave some width at both sides.