The double-walled glasses are made of borosilicate glass, which makes them lightweight yet robust. Beneath the glass bottom, there is a hydrophobic silicone membrane that serves to equalize pressure between the glass walls. This allows the glass to "breathe": with cold drinks, no condensation forms on the surface of the glass, leaving no unsightly water rings. These glasses are also ideal for serving ice cream and other desserts. Made from double-walled borosilicate glass for better insulation performance: hot beverages stay hot longer and cold ones stay cold longer. No condensation forms with cold drinks, so the glass also leaves no unsightly water rings. There is no risk of burning your fingers with hot drinks – even without a handle. The glass is mouth-blown and stackable.