KFI Green Line FiltersThe 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 250 3250 CFM . Our filters consist of only 2 things, steel and carbon;