FRS-30 coarse filter cotton 1,Washable and reusable 2,Low initial resistance 3,Large dust holding capacity FRS-30 coarse filter cotton ·Washable and reusable ·Low initial resistance ·Large dust holding capacity ·Flexible ·Economical and practicalApplication: ≥5μm, Filter dust , (especially used in the train or the subway, where the place has air-conditioner), pre-filter through air filter ...