This 3 inch diameter wide hood mouth hood is contractor grade, heavy duty construction that has a limited lifetime warranty. The hood louvered dampers operates quietly for maximum exhaust air flow and seals when not in operation to help prevent back drafts. The bathroom vent hood has a melting point of 325 F. The bathroom hood is flexible, easy to install. The bathroom vent should be self-cleaned with wind or rain. The bathroom duct's bird guards helps prevents birds and rodents from entering home through your bathroom vent.