Winflo carbon filters / charcoal filters 2 piece set is designed for ductless range hood installation. Please look at manufacturer's listing on the range hood and/or range hood listing before purchase to ensure this filter size fits your range hood. They are attached to the range hood blower to clean the air before recirculating back into the house. Duct work is not necessary. Winflo carbon filters are the solution for the kitchens that don't have an exhausting duct option to the outdoors. This carbon filter fits SOME of Winflo wall mount and island mount range hoods. For use only in Winflo range hoods.