These filters are disposable! Filters in your CPAP machines are a very important part of your sleep therapy as they serve to remove dust and pollen particles. They can be used for the Respironics LX Series CPAP machines, and the Solo LX, Solo Plus LX, Aria LX, REMstar LX, and Virtuoso LX CPAP machines. The package includes 2 filters measuring 2.25 inches long and 3.25 inches wide. If you are unsure of the right size filter just give us a call.