The F1 HEPA Filter for Royal Dirt Devil Vacuum Cleaners helps capture dust mites, grass and ragweed pollen. The filter is compatible with select Royal Dirt Devil upright vacuum cleaners. This filter should be changed every 6 to 9 months to keep vacuum performance at its best. Fits a variety of bagless uprightsTraps 99.97 percent of dust and pollen down to 0.3 micronsSlightly tapered: 3.25 inch in diameter at the bottom, 2.75 inch in diameter at the top