The complete ONA Carbon-Air is the latest in environmentally friendly odor control! It has two 6″ ports to facilitate airflow into the carbon filter and out through the fan unit, and comes complete with bituminous charcoal based carbon filter with one 6″ inch duct for incoming air (top duct), gel, and 450 CFM fan??with one 6″ duct for outgoing air (bottom duct).??Connect to existing ventilation system to distribute throughout room or air exhaust system. ONA Gel attaches securely to the bottom of the Carbon-Air unit. To be used exclusively with ONA Gel.