The DryerJack is the first roof vent designed to meet the more stringent venting requirements of dryer exhaust systems. DryerJack affects airflow by less than .01 water column inches of pressure. The position and curvature of the damper, combined with hood size and collar placement, optimize airflow to such a degree that laboratory tests confirm nearly zero reduction in airflow. At less than 5 1/2" above the roof plane, it is also low-profile for minimal visibility. This model has been discontinued for the new DryerJack Model DJ477. There is a limited supply left in stock of each finish.