I am looking for a place to order a thimble sizer to go from my 6" stove pipe into my 8" clay thimble. I read on an old post of Elmer's pipe but couldn't get their site to work. These seem to be the best option for going into my current thimble. I believe it is a doughnut looking thing that centers up the 6" inside the 8" and seals it up. Thanks