This is a device designed to control the airflow on tanks. If you are using a tank or other device where the hit is thin then this is the solution. The Airflow Controller serves to cover the airflow notches increasing the resistance felt when taking a draw off of your electronic cigarette.
The Airflow Controller screws onto the 510 connector of your electonic cigarette. Attach the Controller first and then attach your tank. With the Controller screwed on all the way down the airflow notches are unimpeded. But as you unscrew the Controller it rises up and starts to cover the airflow holes on the tank. You can adjust it all the way until it is snug under the tank.