Most coffee drinkers would agree that a good cup of coffee can- and should be- had at any time, but they will likely also say that hot or cold coffee has a short perfect temperature life. Hot coffee must be hot, and ice coffee must be cold. To give our dedicated coffee lovers a cup suited to their needs, we created the Declan coffee mug to best hold the coffee's ideal temperature. Following our Declan 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 four mugs are made of pristine hand blown glass that can withstand a temperature of up 350 degrees Fahrenheit; this heat can be from the microwave, the liquid itself, a dishwasher or even an oven! Similarly, our Declan 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. Declan Irish mugs are must-have additions to your cabinets that, at JoyJolt, we know will significantly improve your coffee drinking experiences.