The twin wall interfacing baffles of this John S. Dull 20 in. x 20 in. Hood Filter separate grease and air, making an effective barrier. The smooth galvanized surface encourages constant grease run off, depositing grease in collection troughs. The grease running off creates a safer work environment in which the danger of a grease fire is drastically reduced. Due to the metal design, this filter can easily be washed to create the safest work environment possible. Height measurement is direction of baffles. - Galvanized Steel - NSF and UL listed - Width 20 in - Height 20 in - Sold per each