... .Reused 3.G4 efficiency 4.Color ,White, Supply 5 mm Pre Air Filter Material Features1.Using polyester, polyamide, nylon, etc. ... be with galvanized steel or aluminum alloy frame and also expanded metal on the exhaust side, to effectively prevent deformation of ... as prevention and controof pollution, filtration of fresh air, pre-filtering prior to medium efficiency filter efficiency filter, as well ...