4”x8” Funk Filter Carbon Air Filter. 150 CFM Funk Filters consist of an aluminum housing packed with a high performance virgin activated carbon. These are available in a wide range of sizes making them ideal for smaller tents and large commercial greenhouse applications. They remove 99.5% of all odors and most other airborne particles to keep your plants safe. The granular carbon has a 1050 mg/g iodine number providing more surface area and thus a longer filter life. The extra efficient 2 inch carbon base and aluminum housing provide an ultra-light filter that is easier to handle, yet out performs many heavier filters.