This is a Septic Odour Filter, you install it onto your vent stack. There is a mesh filter near the bottom of the filter where the  activated charcoal will sit and absorb the gases from the vent, so there's no more outside septic smells... It has a metal rain cap and plastic housing. Can be fitted to any ​size vent pipe. Very easy to install, no gluing, cutting or drilling. Just fit the unit on your vent pipe. It's made in Canada and it's very durable and will last for years.