Old Big Vents

We have had a rash recently of orders that unfortunately require the custom M vent for 4 and 5 inch diamter vents. If your home was built prior to 1960 or has a metal vent, especially cast iron, you probably have a 4 inch vent in which case you need to order a M vent shield. These are custom so we will need to know some information before we can make you one. Please bear this in mind when ordering