DeVilbiss brand OEM #DV51D-603 disposable white ultra-fine filters that are used by the DeVilbiss IntelliPAP CPAP, Auto CPAP machines, and BiLevel machines. Use thes filters to remove very fine particulates (as small as 0.3 microns) from your machine's air stream. These filters should be installed behind the standard gray foam filter.
Four filters per pack.
