For the Puritan Bennett Goodknight 418 CPAP machine, these disposable CPAP filters come 4 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.