The Pro Guard 7 filtration system by Advanced Filtration Engineering is the only washable/reuseable filter that stops the dirt as well as an OEM paper filter. Pro Guard 7 technology consists of 5 layers of medical quality gauze instead of the typical 4 layers and each layer is a progressively finer weave of material. Each layer attracts and captures smaller and smaller dirt particles. Finally the last two layers are a non-woven synthetic polyester fabric with a randon porosity. The use of aluminum screen on both sides of the filter media completes the filtering media. The frame of the filter is made from polyurethane to exacting dimensions. The edge of the polyurethane frame does not "flow" into the filtering media providing the truck with more air flow as compared to the competitions moulding process. If you want the maximum flow but not the dirt Pro Guard 7 is your only option.