1.Use: Comfortable ventilation and air conditioning system of the filter 2.outer frame: aluminum alloy or galvanized, 21mm thic 1.Use: Comfortable ventilation and air conditioning system of the filter2.outer frame: aluminum alloy or galvanized, 21mm thick flange3.filter material: Molten spray superfine synthetic fiber filter material, "v" type filter bag structure4.inner frame: Galvanized wire or ...