Unlike standard cab filters that have only a paper-like medium to trap dusts, our three-stage filter combines dust filter mediums (Stage 1) with activated charcoal (Stage 2) which adsorbs pesticide and other organic vapors and traps pollen and molds. A final filter (Stage 3) reduces the amount of charcoal fines entering your cab, so you breathe cleaner air. Each filter is housed in a durable metal case and is designed to fit snugly in your tractor cab. Replace filters annually or when you begin to again taste or smell chemical vapors. NOTE: Custom filters may be available, on a special order basis, for Anhydrous Ammonia (NH3) . Please call us and we will check for you (4-week lead time) . WARNING: Our Clean Air Filters are not a replacement for wearing personal protective equipment, as required by many pesticide labels. Also, this filter may reduce airflow in your cab. Fits FORD: SQUARE CABS Series 2, 7710-8830 models (requires 2 filters) . Dimensions of filter: 3.94x18.31x3.16. Replacement Filter for manufacturer9;s filter: E4NN94000-N20AF.