The Respironics Ultrafine Disposable Filter can be used in all full sized DreamStation CPAP and BiPAP machines. This filter is ideal for homes with a lot of dust, tobacco smoke, or pets. This filter helps clean the air you breath, as well as keeping dust and debris away from the DreamStation motor. The DreamStation uses a reusable blue pollen filter and this light-blue ultra-fine filter that is disposable. The reusable blue filter screens out normal household dust and pollens, while the light-blue ultra-fine filter provides more complete filtration of very fine particles. The reusable blue filter must be in place at all times when the device is operating. The ultra-fine filter is recommended for people who are sensitive to tobacco smoke or other small particles. This filter should be replaced every month and comes in a pack of two or a pack of six.