Copkim 2 Pcs 4 Inch Backdraft Damper Inline Spring Duct Draft Stopper One Way

A pair of backdraft dampers sized for 4-inch round ducts. Each one sits inside the duct and lets air flow in one direction only, which helps keep outside air, cold drafts and pests from drifting back through the line. They suit dryer vent runs and similar spots such as bathrooms, garages, sheds and range hood ducts. Internal rubber seals reduce rattling as the blades move, and an outer foam strip holds the damper snugly in place once it is pushed into the duct end. The body is galvanized steel, with aluminum blades and stainless steel axle and spring. Installation is a simple push fit. These are meant only for metal ducting and will not fit plastic pipe, so measure your duct diameter before ordering.