Supply Air inlet Pre Filter ,Filter cotton 1.100% polyester 2.Reused 3.G4 efficiency 4.Color ,White, Supply 5 mm Pre Air Filter Material ... repeatedly6.Can be with galvanized steel or aluminum alloy frame and also expanded metal on the exhaust side, to ... and controof pollution, filtration of fresh air, pre-filtering prior to medium efficiency filter efficiency filter, as well as filtration of return ...