UNIQUE HAND-BLOWN BOROSILICATE GLASS: our glass coffee cups are made from hand-blown borosilicate glass so that the glass is stronger and has far fewer defects. It is more durable than normal glass and is well known as the purest and safest material to contact with water. CONDENSATION RESISTANT DESIGN: The insulation effect of the double-walled design keeps your iced coffee cold longer, and the thermal properties of this design virtually eliminate condensation on the outside glass.