The Helios ELF-KWL 270÷370÷4÷4 BP is a replacement air filter specifically designed for the bypass section of the KWL EC 270 and KWL EC 370 W ventilation systems. Classified as G4, it efficiently captures coarse particles, helping to maintain airflow quality and system protection. This set includes two filters, providing an easy and effective solution for continued reliable ventilation performance.