The Aspire ET-S BDC is a new bottom coil clearomizer featuring dual heating elements and pyrex glass to provide twice the vapor. It is constructed of metal and pyrex glass. The outer metal casing protects the pyrex glass but includes a window so that you can see your e-liquid level at all times. Also the tank has a capacity of just under 3ml of e-liquid and it comes pre-loaded with a 1.8ohm dual coil head.