Special cartridge filter for both wet and dry pick-up. Maintains suction power even when used with fine debris like drywall dust. Resists clogging, easy to clean, just tap or rinse, reusable and has exclusive nonstick surface. Fits full size vacs. Does not fit Hang Up Vacs, 5 Gal Contractor Portable, Floormaster Plus, All Around Plus, Heavy Duty Portable, 1x1, BullDog Portable, Mighty Mini, Mini Hangup, Hippo, or All Arounds with 1-1/2 or 2 Gal tank sizes.