JoyJolt double wall glasses are mouth-blown by expert artisans using borosilicate glass. Borosilicate is stronger than traditional “soda-lime” glass and can be used for everything from drinkware to cookware. Due to the natural properties of the boron particles, the glass is held together tighter, resulting in a stronger, lighter glass. Borosilicate glass doesn’t need to be as thick as traditional glass to be just as strong due to the bonding capability boron oxide. Your JoyJolt Stoiva double wall glasses arrive as a set of 4 and holds (5 oz.) each. They are securely packed in a beautiful gift box and are the perfect gift for yourself or anyone who enjoys fine drinkware. Because we specifically designed our cups to make sure you can enjoy your espresso just the way it is supposed to. Espresso is meant to be served piping hot, as soon as it’s taken off the espresso machine, so our glass cups feature a double-wall thermal insulation that keeps drinks hot for extended periods of time, so your coffee tastes amazing from the first sip to the last.