Mylar® OL13AT is a biaxially oriented polyester (OPET) film with an amorphous polyester heat seal layer. It is used as a heat sealable lidding film in packaging refrigerated and frozen foods. Mylar® OL13AT is dual ovenable film which provides very strong, aggressive seals to polar substrates such as amorphous polyester (APET, also PETG), semicrystalline polyester (CPET), polyester coated paperboard, and polyvinylchloride (PVC). Mylar® OL13AT does not seal to polyethylene, polypropylene, or polystyrene. DuPont Teijin Films offers another family of lidding films (RL types) for sealing to these substrates. Mylar® OL13AT is similar to OL12AT but has a thicker seal layer than Mylar® OL12AT to give enhanced seal strength. In general, Mylar® OL13AT can produce non-peeling, near "lock-up" type seals and is recommended for hot fill applications where non-peeling seals are desired. It can also be used in some "post-pasteurized" (steam sterilization) applications where the pressure balance in the package can be properly controlled (via vacuum or overpressure). Mylar® OL13 lidding films have excellent grease and oil resistance.

Mylar® OL13AT lidding films are available with anti-fogging capability to provide better clarity when stored and displayed in refrigerated conditions. This film type is marketed by DuPont Teijin Films as OL13AT and is available with corona treatment on opposite side of film from the heat seal layer.