GeneralAire AC-4 Replacement Air Filters (2-pack) Original GeneralAire replacement filter for GeneralAire air cleaner. Filter comes shipped like a collapsed accordian. Filter must be expanded into existing frame using existing pleat spacers. Expanded Dimensions: 15 3/4" X 23 1/4" X 4 3/4" OEM replacement for GeneralAire AC-4 Furnace-mount air cleaner.