CSF 16-18 Ford Focus RS RadiatorThe 42mm 2 Row aluminum core is a massive improvement over the factory core. A thicker core, second cooling row, and increased fluid capacity drastically improves the amount of heat the system can absorb and dissipate. CSF's Exclusive B Tube Technology increases the heat transfer by approximately 15% over regular oval welded tubes. In addition, the super efficient multi louvered fins maximize airflow through the core for the best possible cooling