●It is divided into two kinds: frame bag type; 
●G3 White, G4 green and white; 
●Low initial resistance, good air permeability, large volume of dust; 
●can be cleaned and reused; 
●Economical and practical.
●Clean the system of clean room and air-conditioning of fresh air, pre-filtrate air, new vent, etc. 
●Central air-conditioning system primary filtration, air-conditioning purification equipment fresh air vent pre-filtration;
●Pre-filter of medium effect filter;
●Do the first or second level filtering in all filter systems.
●Filter Material: Initial effect spray filter cotton, G3 white, G4 light green;  
●Sub-frame: Galvanized folding frame, stainless steel folding frame, white paint folding frame;  
●Frame: No frame, galvanized box, aluminum frame, stainless steel frame; 
●Features: Multi-bag design, large ventilation volume, washable filter material, frame and iron frame can be reused. (Recommended repeat times in 3 times)