Mylar® RL42 (formerly known as XM985) is a biaxially oriented polyester (OPET) film with an ethylene vinyl acetate (EVA) heat seal layer. It is used as a heat sealable lidding film in packaging frozen and refrigerated foods. Mylar® RL42 is designed to produce strong seals to polypropylene (PP). Although designed especially to seal to polypropylene, Mylar® RL42 seals to a broad range of container substrates including amorphous polyester (APET, also PETG), semicrystalline polyester (CPET), polyester coated paperboard, polyvinylchloride (PVC), polyethylene (HDPE), and polystyrene (HIPS). Mylar® RL42 has the same heat seal layer thickness as Mylar® RL32, but produces a stronger seal to polypropylene. Mylar® RL42 can produce tearing seals to polypropylene and other substrates under chilled conditions. Like the other "RL" types with EVA heat seal layer, Mylar® RL42 has a lower seal initiation temperature than lidding films with an amorphous polyester heat seal layer (e.g., Mylar® OL, OL2). This allows good seals to be made at higher line speeds (or using lower sealing temperatures).