Disposable CPAP filters for all the Puritan Bennett Goodknight 420 Series CPAP machines, including the 420G, 420S, and 420E, and the Puritan Bennett. Goodknight 425 and 425ST Bi-level machines. Two CPAP filters per package.Ultra fine, disposable CPAP filters are an essential component for your CPAP therapy due to their ability to remove irritating dust, pollen, and tobacco smoke particles from your CPAP airflow. Not sure which CPAP filters fit your machine? Please call CPAP Supply USA for help with choosing your CPAP filters.