Mylar® RL43 is a biaxially oriented polyester (OPET) film with an ethylene vinyl acetate (EVA) heat seal layer. Mylar® RL43 is designed to produce strong heat seals to polypropylene (PP). Although designed especially to seal to polypropylene, Mylar® RL43 will produce strong 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® RL43 has the same type heat seal layer as Mylar® RL42, but the seal layer is thicker than Mylar® RL42. Mylar® RL43 produces the highest seal strengths to polypropylene of Mylar® lidding films and tends to produce tearing seals to non-polar substrates under chilled conditions. Mylar® RL43 is recommended when light caulking is needed. Mylar® RL43, like other RL types, 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).