Borosilicate glass is a type of glass with silica and boron trioxide as the main glass-forming constituents. Borosilicate glasses are known for having very low coefficients of thermal expansion (≈3 × 10−6 K−1 at 20 °C), making them more resistant to thermal shock than any other common glass. Such glass is subjected to less thermal stress and can withstand temperature differentials without fracturing of about 165 °C (329 °F).[1] It is commonly used for the construction of reagent bottles and flasks.

Borosilicate glass is sold under various trade names, including Borosil, Duran, Pyrex, Supertek, Suprax, Simax, Bellco, BSA 60, BSC 51 (by NIPRO), Heatex, Endural, Schott, Refmex, Kimax, and MG (India).