The Polini air filter sponges have two layers. The first layer has medium sized pores to filter rough dust particles. The second layer has very small pores that can also filter dust particles of microscopically small size – it’s these that cause the major damages. The filters are made of self extinguishing polyurethan foam. Their two layers are joined together by means of a special hot forming process which does not manipulate the filtering properties. The outer rough layer is made of black filter material: open polyurethane foam with a permeance of 30 ppi (pores per inch). The fine-pored second layer comes in blue filter material: open polyurethane foam with a permeance of 60 ppi (pores per inch).

The rippled outer surface of this performance air filter element facilitates an increased flow of air, with at least 50% more air being filtered than with more common types.