It’s about a 9 inch by 9 inch hole. 8 inch chimney and pipe is 8 inch into 7. Stove piping is about .040 inch thick. Tension of the wall ring is and height of the stove pipe holds the 8 to 7 inch reducer in place. Has a 1 to 2 inches of some type concrete but not a crock. This concrete rings appears to sit in some of material that looks to be a pale white material not sure if it’s wood but kind of looks like it’s not. House built in 1980. Thanks.
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![[Hearth.com] Is this masonry pass through safe? [Hearth.com] Is this masonry pass through safe?](https://www.hearth.com/talk/data/attachments/293/293636-586f4fd013b6c22f7bc652622a26697b.jpg?hash=KbAXQDz53s)