Product review (2 stars): A real cruddy product
Great product from a sellers viewpoint.  Suck the customer in then sell them more cruddy product.  If you pull the black stuff off the back when washing the filters that eliminates the black mess.  Too bad this filter is not sold as a reusable like some the blue reusable holmes 750 filters are.  But that would make too much sense.  BTW the standard reply from the manufacturer that they will let the product development team know is a crock.  I even tried to call the supplied phone number and that takes you down a endless rabbit hole.  But now that I am "locked in" to the wemo I have only one choice
keep buying their cruddy replacements or think up a way to make my own.  I am experimenting with using bath towels sewn into the correct size and thickness with a thin wire frame or screen to keep them fairly stiff. these could be washed in the machine.  Will update you in a while. Meanwhile I will keep washing these out rather than fork my money over to these folks/