The Hypo-Allergenic CPAP filters are designed specifically to be used with the ResMed AirSense™ 11 CPAP machines and add an additional layer of protection from pollutants.  The length, width, and height are specific to these devices and allow the air to be properly filtrated by the machine. The machines pull from the room air when providing the user a positive airway pressure and the filter is the last line of defense for air pollutants.
 
Note: a dirty or clogged filter can cause the machine to malfunction and in some severe cases cause complete failure.