These open cell polyester foams are commonly used in filtering applications. They do not swell when in contact with water, fuel, soaps, detergents, mineral oils or greases. However, most of the organic solvents will cause swelling. They are available in various porosity grades, measured in PPI (pores per linear inch). The greater the PPI of the foam, the greater resistance to airflow the filter offers. Supplied in 2mtr x 1mtr sheets, our standard Reticulated Filter Foam grades available are 20, 30, 45 and 60 PPI.