The double-wall construction is more than just practical, it makes the cups elegant and unique. As you can see from the photos, it make it appear as if the beverage is floating suspended in the cup. This effect is especially beautiful with teas and herbal infusions, which often have a subtle and beautiful color to them. Why drink those beverages from a opaque mug when you can put them on display in a beautiful insulated glass? Additionally, these cups will survive in a dishwasher for easy care. They also included a lab test showing that they are low in leachable lead etc.