The Quad-Flex RDA configuration supports dual or single airflow. The Quad-Flex comes with two adjustable airflow sleeves. There is a top airflow and a side airflow sleeve. Interchange according to your airflow preferences. Aspire Quad-Flex Squonker a.k.a. bottom feed RDA is the first of its kind. Just change out the RDA screw with the bottom-feed capillary screw and start squonking. Use the top-airflow sleeve when squonking. Aspire’s innovative new squonker screw there is sufficient capillary action to return the excess e-liquid to the bottom tank.