The PET is heated and placed in a mold, where it assumes the shape of a long, thin tube. The process by which the plastic is forced into the mold is called Injection Moulding. The tube of PET is then transferred into a second, bottle-shaped mold. A thin steel rod is slid inside the parison where it fills the parison with highly pressurized air, and stretch blow molding begins: as a result of the pressurized air, heat and pressure, the parison is blown and stretched into the mold, assuming a bottle shape.
To ensure that the bottom of the bottle retains a consistently flat shape, a separate component of plastic is simultaneously joined to the bottle during blow molding.