In line filter cleans the air leaving a CPAP or BiPAP machine. It is used with the machine's built-in inlet filters to provide clean air. Male Connector End Outer Diameter: 15mm. Female Connector End Interior Diameter: 22mm. Fits 22mm tubing machine. Quick and simple to install and replace. The filter attaches between the machine's air outlet and the CPAP hose. Efficiency: 99.99% or higher. Latex free. Each filter is individually sterilized and sealed. Color: white. Material: plastic. Package contents: 12 filters. Only the above package content is included; other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture to appear slightly different from the actual item. Measurement may vary by +/- 1-3cm.