Improve your HVAC system's performance with this durable Return Air Filter Box with Filter Rack, designed to fit a 17.5 inch wide air handler and C cabinet air handler. Constructed from 24 gauge galvanized steel, this air box measures 21.13 inch L x 21 inch W x 22.5 inch H and supports a 20x20x1 filter for efficient air filtration and airflow. Ideal for residential and commercial HVAC applications.