Check the listing for details. Universal Inline Bacterial Viral Filter for CPAP Machines New 1 Pcs. Color: Clear/Blue, Condition: New with box. Listed at 8.69 USD. 1 pcs - Universal Inline Bacterial Viral Filter for CPAP & BIPAP Machines New This filter offers over 3 times the filter media compared to a round filter. This allows for better airflow and longer filter life. Will fit standard 22mm CPAP hose. You just need connect the filter to cpap machine between the air outlet and your heated tubing or mask elbow. Compatible With Most Cpap Machines: Fit In-line filter for 22mm tubing machine and 25mm mask elbow. This filter is meant for single use. This filter should not be cleaned or washed. Should be changed about once every month unless the filter is starting to look dirty or airflow is reduced. COMPATIBLE WITH RES-MED, PHILLIPS MACHINES: This filters will fit almost every machine with 22mm tubing7/8" (22mm) ID & 15/16" (25mm) OD25/32" (20mmm) ID & 7/8" (22mm) ODBin 501 & 502