These HypoAllergenic Disposable Filters are made of non-woven acrylic and polypropylene fibers with a polypropylene carrier. The combination of materials helps block even the very finest of partibles. They are compatible with all S9 Series CPAP/BiLevel machines, all AirSense 10 Series CPAP Machines, and all AirCurve 10 Series BiLevel Machines.