AeraMax PRO AM3-4 50mm Carbon Filter with Pre-filter, Pack of 2Commercial grade Activated Carbon Filter absorbs a wide range of volatile organic compounds (VOCs) and odours. Includes separate Pre filter to capture larger particulate to help extend life of subsequent filters. Compatible with Fellowes AeraMax PRO AM3, AM3S, AM4 and AM4S Air Purifiers. Replace the Carbon Filter approximately every 12 months, depending on usage conditions, in order to ensure that the Air Purifier remains effective. Pack of 2 Carbon