A set of two elegant double-walled coffee mugs. Made from chemistry-grade borosilicate glass. The double-walled design insulates the mug, keeping your beverages hot or cold longer. You'll love the pleasing optical effect of the liquid floating in air inside the cups. They are made from durable hand-blown glass and present far fewer defects, if any, compared to other glass mugs. And they are backed by a lifetime warranty, so you'll receive high-quality mugs you'll enjoy for years to come.