Aspire ET-S Tank
The ET-S Glass version BDC is an upgrade version of ET BDC, it has an exterior metal sleeve surrounding the tank with two small windows that allow you to see how much liquid is left in the tank at all times.
It is a clearomizer made of glass and metal. These types of clearomizers are commonly refferred to as "Glassomizers" (a clearomizer but with glass walls).
1 Aspire ET-S tank with a 1.8ohm BVC coil installed