Plastic material in the form of granules is subjected to heat and pressure in an extruder. Semi- molten plastic in extruder passed through the nozzle known as parison. Adjustment has to be made in the machine to vary the wall thickness of the parison. Suitable parison is then inserted in a female mould and air is blown into parison to force the molten plastic against the sides of the mould. The material is then cooled before removal from the mould. The article is then trimmed to remove flashes. Moog technology is used to have even wall thickness.