Double Wall Insulation - The double walled design of these tea cups aims to provide optimal thermal insulation for any and all beverages, preserving their temperature longer as well as avoiding you any nasty burns.  Heat Resistant Borosilicate Glass - In creating these cups, Charbrew has used laboratory standard borosilicate glass so as to ensure that they are both durable and thin. As a result, these glasses are safe to go in the freezer. Avoid using in microwave and washing in dishwasher. Ideal Size For Daily Use – Coming in at a volume capacity of 250ml, the Charbrew duo of tea cups will hold enough beverage to quench any thirst. Colossal Cappuccino and minute Macchiato, into these cups hot and cold beverages throw. Multi-purpose -  The strength of the double walled tea cup lies in its flexibility of function – it will as happily serve for tea as it might for ice cream or smoothies. Charbrew Double Walled Glass Thermo Tea Cups - Pack of 4 250ml Cups for Tea, Coffee, Ice Cream