Canteen Double Wall Thermo-Glasses keep hot drinks hot without burning fingers and cold drink cold without messy condensation, making them the ideal vessels for every beverage, from cocktails, to cocoa. So you'll only need to buy one type of glass for your home! Individually mouth-blown by expert artisans. Two walls of borosilicate glass, creates a highly effective layer of insulation. Silicone valve at base allows for changes in pressure. Dishwasher and microwave safe. Oven safe (up to 350°F/176°C).