Flush fit register booster increases airflow to under-performing registers improving comfort in rooms that are too hot or too cold. Works automatically with forced air systems. The quiet, 3-speed dual fans pull extra air out of weak registers, boosting airflow by up to 85%. Push button function controls. Fits a 4" x 10" wall or floor register by simply replacing the existing wall or floor register. 12V (volt) - safe for children and pets. 6' cord. 1 year limited warranty.