Truma heater cowl extension

I recently discovered that in order to safely use the gas heater in my Eriba "pop top" caravan I need an extension on the flue of the gas heater so that the burnt gasses exit above the roof line and not blow back inside. The extension is just a piece of plastic tube threaded at each end. It fitted fine, and is as expected. Just need to remember to fit/remove it when needed!