The Disposable Ultra-Fine Filters are for use in the Philips Dreamstation CPAP machine. These filters come in a pack of six (6). The disposable filter is housed in a light blue frame and blocks fine particles. It can be used in conjunction with the reusable dark blue filter already included in your machine. These disposable ultra-fine filters can not be washed and must be replaced regularly. These filters are to be used in conjunction with the dark blue housed filters that are included with your machine, these are located under the flap on the right-hand side of the machine.