If you look around at the products that use PET bottles, you can see a clue: PET bottles can hold not only liquids, but also solids. Plastic blow molding machines are used in factories that produce these products, including:
Pharmaceutical industry
Food industry
Beverage industry
Cosmetics industry
Daily chemical industry
Snacks and nuts
Of course, packaging companies that provide PET plastic bottles for the above industries can also use PET blow molding machines suitable for mass production.