The HART foam wet filter enhances your wet/dry vacuum's liquid spill cleaning capabilities. The VFF51 3701 model is reusable and compatible with 5 to 20 gallon HART wet/dry vacuums and most other standard wet/dry vacuums of the same size. Its standard design ensures quick and easy installation by simply sliding the filter over the filter cage. It's designed for wet pick-up only and comes in a 1-Pack. Avoid using the filter for hazardous, toxic, or burning materials, such as cigarettes, matches, or hot ashes.