Following our Caleo's telltale design, the coffee mug in this series has a double wall application to maintain your drink's hot temperature while protecting your hands from the heat. The set of two 13 oz. mugs are made of pristine hand blown glass that can withstand a temperature of up 350° F; this heat can be from the microwave, the liquid itself, a dishwasher or even an oven. Similarly, our Caleo mugs are freezer safe, allowing hot coffee to be turned iced without having to change cups. By using only top quality borosilicate-glass for our mugs, we are able to give our customers durability, functionality and style all in one. Caleo mugs are must-have additions to your cabinets that, at JoyJolt, we know will significantly improve your coffee drinking experiences.