OdorHog Vent Pipe Filter Black ABS w/Mushroom Cap ((3.0) Inch) Eliminates offensive outdoor odors from the roof vents. Not for use if you have an indoor odor. For PLASTIC vent pipes, NOT METAL OR CAST IRON vent pipes. Made in the USA. Ships USPS PRIORITY 2 or 3 DAY to most US zip codes. Superior carbon! Lasts years, not months...Installs in seconds, no glue, no tools. NOT RECOMMENDED FOR Mobile Homes, Modular Homes, Homes with a bathroom remodel, Historic Homes, Homes with an indoor odor or plumbing issue. PLEASE MEASURE YOUR PIPE BEFORE ORDERING. See graph on how to measure.