Borosilicate glass is a type of glass that is mostly composed of silica and boron trioxide. Borosilicate glasses have much lower thermal expansion coefficients than most common glasses (≈3 × 10−6 K−1 at 20 °C), making them very resistant to thermal shocks. Such glass is less thermally strained and can withstand temperature fluctuations of up to 165 degrees Celsius (297 degrees Fahrenheit) without cracking. It's used to make reagent bottles and flasks, as well as lights, electronics, and cookery.