Bodum's insulated glassware is made from durable Borosilicate glass. Borosilicate glass is a strong heat-resistant glass that weighs less than traditional glassware. It is important to explain that Borosilicate glass doesn't need to be as thick as traditional glass to be just as strong. Borosilicate is simply a different type of glass that is resistant to temperature swings and scratching. Because the particles are held together so tightly, borosilicate glass is dishwasher safe and will not become cloudy over time. Simply treat it as you would any glass product and it will stand up to every day use. Dishwasher & microwave safe. Our insulated, double wall glass is handmade by expert artisans. Please use care when placing ice into the glass to avoid fracturing the inner layer. Please also avoid using metal spoons or placing the glass into a crowded dishwasher. These glasses will help to keep hot drinks warmer and cool drinks cooler.