These filters are expertly designed to fit perfectly within the F&P SleepStyle 234, 244, and 600 series CPAP machines, ensuring easy installation. Thanks to their complete coverage and ability to block even ultra-fine particles, these filters allow each machine to provide clean air to the patient. Replace the used filter every three months or whenever it appears discolored or soiled. Do not wash the filters. Sign up for a Sleep Club Subscription to easily replenish your stock of filters and other supplies! Subscriptions begin at $45 a month and include all of the equipment you will need, delivered exactly when experts recommend.