Note - This review is for the circular 6 inch size cap. It fit snugly down into the inner flue stovepipe on our chimney location above our family room Franklin stove. However, unlike the cap it replaced, it did nothing to seal or cover the space between this inner pipe and the outer one. Other designs we have used had a collar at the bottom to cover this area. I will have to fashion something to cover or close this circular space to stabilize the inner pipe and new cap, and prevent water, insects or debris from entering between the layers. Also somewhat concerned that the large gauge screen does not completely cover the opening, allowing insects, snakes or other critters to still get into the pipe with the cap on, and fall down into the stove. We have caught quite a variety of things over the years. I may have to add some additional screen to this area as well.