The automotive radiator uses a thin foil material that is rolled into a corrugated pattern to transfer heat from the cooling tube to the air. Small windows or louvers are embossed into the foil during roll forming. The blinds form a group on half of the material and then form a mirror on the other half. When the air passes through the radiator core, the louvers deflect the airflow in an S-shaped or serpentine pattern. As a result, the term "serpentine" was employed. The louver pattern, angle and width can have a specific effect on heat transfer.