Usage: pre-efficiency air purifier filtration for absorbing smoke, dust and other 0.5um particulars Feature: low resistance large dust holding capacity easy to wash Frame(optional): Plastic(PP or ABS) aluminium frame water-proof paper frame size: as customization Filter media (optional): PP or PE mesh Pre-efficiency cotton other function cotton static media Seal strip (optional): EPDM( high resilience) EVA ( high resilience) PU (high density)