Flanders PrecisionAire HR20240 20" by 240" by 1" Hammock Roll Air Filter (1 Pack) Last up to 30 days Effective against the following common contaminants; househould dust, as well as debris and lint Rolls are packaged in convenient carton dispensers UL Class II Available in 1-Inch spun glass, 2-Inch spun glass, and 1-Inch polyester synthetic filter media