10-inch, 6-inch, and 8-inch round, universal make-up air damper kit for use with any Zephyr range hood motor operating over 300 CFM and up to 1,200 CFM, 600 CFM, and 1,000 CFM. When range hoods exhaust air out of your home, negative air pressure is created unless fresh outdoor air replaces the exhausted air. Zephyr’s make-up air damper is designed to balance the air pressure in your home by automatically opening it to allow fresh air while the range hood is operating.