This package contains three reusable dry filters and one filter retainer ring designed to be used in wet/dry utility vacuums made by Shop-Vac Corporation. One is placed over the thick foam filter and the ring slides over it to hold it in place. These are used to provide greater filtration than the thick foam filter alone. While these filters are made by the Shop-Vac Corporation to be used on their vacuums, they will also fit many other wet/dry utility vacuums. For similar products see our list of Generic Wet/Dry Vacuum Supplies.