Replacing the flew pipe when i moved in it was a 6" coupling to a 6" -8" adaptor then 8" to the chimney... i am getting rid of the damper i dont burn coal so i dont need it thinking of going 6" to 8" adaptor 8" pipe to the chimney... my thought better draft my hotblas1557 m that was in the house when i moved in eats wood no matter what in time will be getting an owb but for now this is holding me over