The Wotofo FLOW SUBTANK has a 4ml capacity with a 2ml plug, which can be changed into 2ml capacity and fits for European TPD Policy. Its features in its bottom adjustable airflow and easy top filling, ensuring a good taste and a smooth vaping experience for you. Besides, the atomizer has a 24mm diameter, which is popular in the market. The pin is silver-plated with a good conductivity. The Wotofo FLOW SUBTANK can be compatible with TFV8 Baby coils.