All Pyrex branded cookware used to be made by the Corning company in the US using borosilicate glass. This type of glass has excellent thermal shock resistance, meaning it can go suddenly from hot to cold (or the reverse) without shattering. This original Corning-made cookware has the logo “PYREX in all capital letters. Then, in 1998, Corning sold its housewares division, including Pyrex, to Borden Inc., which marketed the cookware under the World Kitchen name, while keeping the “pyrex” name for bakeware. But note the new logo is all lowercase. Old and new logos are shown in the image.