Lyemance DLEM1313 13" X 13" Energy-Saving Damper

I bought this to prevent my dual flue chimney from drawing smoke/fumes from one opening into the other. Even though I crack open a window to supplement an outside air duct that supplies air into our upstairs fireplace, there must still be a low enough pressure in our house to draw air thru the flue for our lower level fireplace (despite the closed lower fireplace damper). This product is well constructed and fit our standard 12x12 flue tile just fine, and our existing chimney cap was wide enough to fit over the edges of the damper and screw back into place under the outside edges of the damper, though just barely. The damper installed easily with the supplied silicone adhesive, and I was careful to follow other reviewers' advise and uncoil the wire before lowering it down the chimney. The 2 wires shown in the photo join together below the photo, so only 1 wire goes down the chimney. One wire lowers the flapper, the other can engage (by pulling harder on the wire) after the flapper is closed, to actuate a lever that can crack open the other side if frozen shut or stuck. If, like me, you have a functional fireplace damper, you might want to drill a hole in the side of the damper body, and thread the wire end thru it, so the wire won't interfere with closing the fireplace damper. Drilling holes in the firebox for mounting the bracket (to hold the wire taught) is a lot easier with a hammer drill, if you or a friend happens to have one. The wire was 2 ft short for our lower level application (due to 9'ceilings and high roof), so I bought a splicer for 1/16 inch wire at L----'s, added 2+ ft of wire and crimped it with dull wire cutters. Our lower level is now free of smoke odor...

This is one fantastic invention! It really secures my chimney, and I'm noticing a significant change from my old standard damper. The old one allowed cold drafts in and this one does a great job keeping the chimney sealed.
Installation was pretty simple, took me maybe 2 or 2.5 hours. I would definitely recommend installing this yourself, as the chimney sweep quoted me at around $300. Overall, really satisfied.