There's a simple explanation: https://www.allrecipes.com/article/what-is-the-difference-between-two-pyrex-types/ https://www.allrecipes.com/article/what-is-the-

There's a simple explanation: https://www.allrecipes.com/article/what-is-the-difference-between-two-pyrex-types/ https://www.allrecipes.com/article/what-is-the-difference-be... From the EU Pyrex webpage, when they talk about their materials in the French factory, they say it's borosilicate: The Pyrex® glass is unique. It is a borosilicate glass that is tempered, of superior quality and has a great thermal and mechanical shock resistance. [...] The Pyrex® glass is made of pure sand (80%), soda (4%), Alumina (2,5%) and bore (13%). So I'd say that at least EU Pyrex is safer (when talking about thermal shock, I guess). PD: Following the life of Pyrex, Duralex and Saint-Gobain is quite a thing...