The Airbrush Trigger / Push Button is a vital component part of the airbrush air valve and needle assembly. The trigger button opens the airflow valve and moves the needle back and forth smoothly through the airbrush nozzle tip, so that the liquid makeup flows properly. This is a precision manufactured part specifically designed for the "Mist"ique Airbrushes and needles, and made of a strong, durable metal alloy. These trigger / push buttons have a way of getting lost when taking an airbrush apart, so it's best to keep an extra on hand. Your airbrush will not function at all without it!