I have a very old (Montgomery Ward!) vacuum cleaner for the shop. Even with a cleaned foam filter, it spews dust every time you turn it on, which isn't much fun when working with wood. It's getting harder and harder to find paper filters (reasonably priced) to cover the foam and this product did the trick. I like it because not only does it cover the foam, but it is long enough to attach to the plastic above the foam. And because it's Dacron, I can leave it on if I'm vacuuming something wet (which I couldn't with a paper filter bag).