The defining feature of a gravity feed airbrush is the cup mounted on top of the body — integral, threaded or press-fit depending on the model. Siphon feed has to lift paint from a jar below the body; gravity feed places the paint above the nozzle, so it does not need that lift. Paint feeds down as airflow starts and the needle opens.
That arrangement is often used at lower pressure settings, though the usable pressure still depends on the airbrush, paint and airflow. Practically, a smaller hobby cup (often around 1–7 mL, depending on model) reduces paint waste and makes colour changes quicker — convenient for high-detail sessions.
