Fine dust cartridge filter and retainer. Fits 4 gallon Channellock vacuum. It's hard to know what is lurking in your carpets, but you can breathe easy with this durable Channellock Products Filter for shop vacuum cleaners. This compact 5-layer cartridge filter uses media that captures pollens and allergens in the home down to 0.3 microns at 99.97% efficiency. This wet dry vacuum cleaner filter is one tool you'll want working for you. Channellock Products Wet/Dry Vacs recommends replacing your shop vacuum filters at least twice a year to keep your vac working at its optimum level. Fits: Most 4 gallon vacuums.