This is a stainless steel chimney cap and top damper. Top dampers are a way of effectively handling cold air down drafts that occur on masonry chimneys in the winter. the plate fits snugly against the fiberglass gasket.
We also use top dampers to prevent bees from making hives in chimneys, which is a common occurrence.
This chimney cap is rusted at a home along the coast. We replaced the rusted chimney cap.
Broken chimney top in Fullerton that had earthquake damage. We repaired the chimney top.
This is a very beautiful custom chimney cap we built for a house in Long Beach, again out of copper which will patina. We have a very wide variety of ones we can build and install.