The Green Line is Kootenay Filter Inc.’s Lightweight Filter Line. KFI is proud to have a product that uses only virgin activated carbon made from renewable resources. The proven design, manufacturing process and a production staff with years of experience make our product one of the best filters on the market. Our Light line filters are available with flange sizes 4″-14″ rated for 3250cfm. Our filters consist of only 2 things, steel and carbon; they are effective and robust.