These five replacement filter pads are for IQAir's Coarse Dust Pre-Filtration Unit, which protects the fine dust and HEPA filters in IQ units in environments with elevated levels of coarse dusts, such as in dental laboratories or bakeries. You'll want to make sure your air filtration unit is working tip top in areas with high coarse dust, so it's a good idea to keep a spare set of filters on hand. These foam filters are washable and can be reused several times before being replaced, further extending their shelf life.