This replaced an insert. Full oval Duraliner system in the flue. I Installed an 8" oval X 8" round tee and had to jack up the liner system to match the rear flue outlet pipe on the Encore. Little bottle jack under the system and it went right up. Up on the roof to remount the system hanger. Mounted the 1' length transition pipe and coaxed the stove back and the pipe went together pretty easily...amazingly! Everything looks good. Now, I need only one more thing. WOOD