This carbon filter was never used with an original retail price of $38 I decided to dropped it to $25. 4" carbon filter : Activated Carbon Filter: Overall Size: 4" Flange: 10"H x 7"D Flange(optional): 4" Iodine Adsorption Value: 950 (High efficiency) Carbon Layer Thickness: 1.5 inches Specific Surface Area: 900-1000 square meter per gram Max. Endurable Temperature: 400 degrees Celsius (Safer) Operating Environment Temperature: -20 to 65 degrees Celsius zinc-anodized steel housing mesh use Coal Based activated carbon Changeable Velcro Pre-filter with 2 black elastic bands Thick Carbon Layer for Higher Absorption and Performance Exceptional odor control for better privacy. Inner and outer mesh provides 53% open area allowing increased air flow. Machine packed carbon enables 100% filtered air flow. Package includes: 1 x 4" Coal Based Activated Carbon Air Filter