1.filter material: High-quality polyester synthetic fiber 2.inner frame: Galvanized wire supp use:  Use in air conditioning system of primary filtrationouter frame: aluminum alloy frame or outside cardboard boxfilter material: High-quality polyester synthetic fiberinner frame: Galvanized wire supportefficiency:G4(EN779): weight efficiency>=90%continuous operating temperature:<=70resistance to wet:<=100%RHsuggest biggest end resistance:250pa