We've got a Jotul F250, running into 150mm twin wall stainless. I used to have a freestanding Jotul No 7 open fireplace in, but our flue was too narrow, It did work, and kicked out a LOT of heat, but if the wind was from the wrong direction, couch cough cough. It would be lovely in a big inglenook though. Must bung it on Ebay.