The inline filter is compatible with CPAP devices. It works in combination with the machine's inlet filter to deliver clean air. Outer diameter of the connector end: 25 mm. Inner diameter of the female connector end: 22 mm. Compatible with 22 mm tubing. Installation and replacement are quick and easy. The filter connects between the machine's air inlet or outlet and the tubing. For best results: Helps maintain clean airflow for optimal CPAP therapy performance. Set of 6 filters. Free of [restricted substance]. Each filter is individually packaged and sealed. Material: ABS Color: As shown Package Contents: 6 x Filters Only the above package content is included; other products are not included. Note: Lighting and different displays may cause the color of the item to vary slightly from the actual product. Measurement allowance: +/- 1-3 cm.