AF series primary effect filter sponge, a filter sponge with alternate blue and white, is mainly applicable to collecting the larger dust molecules in the air to prevent the medium filter from being filled and blocked with larger dusts so early and to keep long service life and better filtration effect of medium effect and high efficient filter. It’s made of super hard fiber and is sprayed with a kind of adhesive evenly for strengthening. Therefore its hardness and density surpass the similar products, and thus it has better primary filtration effects and larger air flow.