Ok one last question, i got the hole through the foundation big enough now, but I have to enlarge the hole into the chimney/flue too. I'm a little worried though, because the flue itself is 6" wide x 5" long. The opening to the thimble is 6" across, but the entire thing is about 7" across. I'm not sure that this size thimble is appropriate. Do I just get it inside the thimble and flush with the hole in the flue? Or should I be using a smaller thimble?