DeVilbiss Sleepcube Machines Reusable Foam Filters for CPAP & Bi PAP, prevents dust entry Suitable with Devilbiss Sleep cube CPAP/BiPAP Recommended Replacement every 6 months DeVilbiss Sleepcube Machines Reusable Foam Filters for CPAP & Bi PAP, prevents dust entry Suitable with Devilbiss Sleep cube CPAP/BiPAP Recommended Replacement every 6 months