ClearSeal® hinged lid containers are available made of either PET or OPS (see product description for specific materials). Both OPS (Oriented Polystyrene) and PET (Polyethylene Terephthalate) have crystal clarity for superior product visibility as well as being flexible, yet durable, to maximize strength and reliability. PET ClearSeal performs exceptionally in cold temperatures and accommodates freezing down to -22°F.