Fits all Honeywell Round, QuietCare & SilentComfort Series air purifiers; 50000 series, 17000 series, 18150 series, 40100 series, 40200 series & HPA100,200,300 series consoles. (Does not fit HPA towers).. Helps deodorize the air and trap larger particles such as dust, lint, fibers and pet fur. Reduces common household odors with activated carbon. Replace every 3 months. Perforated design makes 1 to 8 pre filters depending on the model.