The Nu-Calgon 4704-24 Filter Housing NP24DD is a durable HVAC filtration housing designed to hold compatible air filters and help maintain clean, efficient airflow. It works by securely containing the filter within the air-handling system, allowing the filter media to capture airborne dust, dirt, and other particles as air passes through. This housing is commonly used with commercial ... https://www.partshnc.com/4704-24-nu-calgon-ice-mach-filter-hsg-np24dd