(3E22) THE AM FILTER, WITH A WIRE FRAME, IS AN EXCELLENT ALTERNATIVE TO CARDBOARD FRAME TYPE AIR FILTERS. THE DRY POLYESTER IS SEWN AROUND A WIRE SUPPORT WITH THE EXCESS MEDIA PROVIDING AN EXCELLENT SEAL AROUND THE PERIMETER OF THE WIRE AND THE HOLDING FRAME.THE POLYESTER MEDIA IS VERY RESISTANT TO HIGH LEVELS OF HUMIDITY. VERY EASY TO INSTALL.