Borosilicate glass is a type of glass with the main glass-forming constituents silica an boron oxide. Borosilicate glasses are most well known for having very low coefficient of thermal expansion (~ 3 x 10-6 / C at 20oC), making them resistant to thermal shock, more so than any other common glass. Borosilicate glass was first developed by German glassmaker Otto Schott in the late 19th century and sold under the brand name "Duran" in 1893. After Corning Glass Works introduced Pyrex in 1915, it became a synonym for borosilicate glass in the English-speaking world (however, since 1998 Pyrex kitchen brand is no longer made of borosilicate but of soda-lime glass).