These tanks are hand blown by a very well known local glass blower here in NM. Each one is custom made and no two are alike. The level of detail and craftsmanship that goes into each one of these is amazing to the point where each one can be considered a work of art. The tanks themselves are made from 4mm borosilicate (also sold under the tradename Pyrex) so they are incredibly strong---much stronger than plastic or acrylic tanks and very heat resistant.
The glass is the perfect medium for using e-liquid that is known to cause problems with plastic or acrylic tanks as it will not crack or absorb the flavor, making switching flavors as easy as a simple rinse in the sink.
Check out this Youtube video for filling and operation instructions: