My chimney had the 13 x 18 clay liners so I had plenty of room to slide the insulated liner down the chimney, my only hang up was the unovalized part get hung up at the smoke shelf. I check the screws on the primary lever and they were tight but I found a few screw that hold in the gasket ang glass that were just a little loose. I have not attched the fan yet but I do have it pulled away a little bit and also figured out that it works better with the control knob on the right side instead of the left side like the way the show it in the pictures. If you install it the way they show it the air flow is blocked by the stove. If you install it with the knob on the right the airflow is not blocked but I do think leaving the gap does let in even more air.