Active Air -Filters offer features and performance that rival the competition - but at a value price. All filters are maintenance free and feature long-lasting activated virgin charcoal that keeps your air odor-free. ACTIVE AIR-FILTERS FEATURE: Corrosion-resistant galvanized steel Changeable Velcro pre-filter to collect dust and airborne particles Shrink wrap to protect the charcoal and keep the filter clean High grade activated charcoal to guarantee maximum odor control Large surface areas and 2.5" thick carbon bed results in optimum odor control and maximum efficiency. No maintenance required Charcoal is carefully packed to insure a consistent and even air flow throughout the carbon bed for a full usage of the filter and its durability Over boxed in corrugated cardboard to protect the filter Recommended airflow: 50 CFM