The Corning Pyrex Borosilicate Glass Flat Bottom Boiling Flask is a 250mL, long-necked flask for heating and boiling liquids. The neck accepts a #5 stopper (sold separately) and has a tooled mouth for a smooth stopper fit. Flat-bottom flasks can be set on a surface. This flask is made of No. 7740 Pyrex brand clear borosilicate glass for durability and chemical- and temperature-resistance, and its uniform wall thickness provides mechanical strength for shock-resistance. Borosilicate glass has a low coefficient of thermal expansion and is resistant to thermal stress. Boiling flasks provide uniform heating of liquids for quality testing, sampling, and research in chemistry, education, research, and life science applications.

Flasks are glass or plastic containers for storing or collecting chemical samples or solutions in scientific laboratories. They come in a variety of sizes and shapes and are designed for a wide range of scientific processes. Erlenmeyer flasks, introduced by German chemist Emil Erlenmeyer in 1861, are shaped like a cone with a wide, flat base that narrows to a neck opening, which can be closed with a stopper or cap.

Corning manufactures consumable glass, ceramics, and plastic laboratory tools under the brands Corning, Costar, Cellgro, Pyrex, Axygen, and Gosselin, among others. The company, founded in 1908, is headquartered in New York, NY.