Genuine Numatic 906421 (Charcoal) Microfresh Filter (160 Drum)Genuine Numatic 906421 (Charcoal) Microfresh Filter (160 Drum) This filter is a Genuine Numatic 906421 ( Charcoal) Microfresh Filter (160 Drum) henry hoover filter product and is the ideal replacement for an old or clogged up filter in your vacuum. I This filter is not washable but should last a long time if you use your vacuum cleaner with genuine Numatic dust bags. The filter should be brushed off during each bag change to get the maximum lifespan