The Original Philips Respironics Reusable Pollen Filters for DreamStation Go CPAP Machine – replacement filter for Philips Respironics DreamStation Go Auto Travel CPAP Machine. These Pollen Filters are used to improve over all air filtration with the DreamStation Go. They are reusable filters and should be cleaned after 2 weeks of use or sooner if they appear dirty. They should be replaced every 6 months an if damaged, it should be replaced immediately. Approximate size is 1.50 x 1.38 inches.