The 4-inch Dust Shroom by Horti Control is like a doorman at a popular bar who is having a bad day; it's not letting anyone through! These reusable HEPA filters are crafted out of foam and will protect your indoor garden, ice boxes, inline fans, ducting, and air-cooled reflectors from uninvited contaminants and pests. Just throw the Dust Shroom into a washer when it gets filled up with pollutants. The Horti Control Dust Shroom has a five-year manufacturer warranty and is made in the United States.