Mylar® RL33 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® RL33 is designed to seal to a broad range of container substrates including amorphous polyester (APET, also PETG), semicrystalline polyester (CPET), polyester coated paperboard, polyvinylchloride (PVC), polyethylene (HDPE), polypropylene (PP), and polystyrene (HIPS). Mylar® RL33 has the same type heat seal layer as Mylar® RL31, but the seal layer is thicker than both Mylar® RL31 and Mylar® RL32. Mylar® RL33 develops stronger seals than Mylar® RL32 to most substrates and tends to produce tearing seals to non-polar substrates under chilled conditions. Mylar® RL33 is recommended when light caulking is needed. Mylar® RL33 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).