PATIKIL 8" HVAC Duct Manual Volume Damper, Metal Adjustment Airflow Ducting Backdraft Damper Control for Air Ventilation System

This assembly is made with relatively heavy tubing. The damper has polymer edge seals, so it can close almost hermetically. The damper blade bearings are superior to those in usual duct dampers. The damper handle is made of stamped sheet metal with sharp edges, so it is advisable to wrap it with duct tape or similar. A potential difficulty is that the diameter of both ends is somewhat smaller than U.S. standard 8". It will fit snugly inside the crimped male end of U.S. duct, but it will have a significant gap inside the plain female end of U.S. duct. Shoving the raised collar of the damper assembly into the female end of the duct reduces the gap. Screws and duct tape should be used at both ends.

The handle could be 1 or 2 inches higher (away from the body) so that the duct insulation can be placed under the handle instead of over it. After I wrapped it up in insulation the handle was no longer visible. If I want to change the opening percentage, I'll have to tear back the insulation for the adjustment. That's the only change I would make. I worked perfectly. I cut it into my 8 inch line and was able to adjust the flow.

This product is very heavy duty and looks like it will outlast my hvac system. I purchased the 8” one. It doesn’t fit tightly into 8” duct work purchased from a hvac supplier. This makes it difficult to connect the ducts together. You will definitely need to seal the joints because there are obvious gaps between the two parts.