Pyrex Conical Flask 250 mL has Brilliant transparency, Superior resistance to chemicals, contaminants, and drastic temperature changes. These are among the key properties that enable Pyrex® glass to endure even the toughest laboratory environments, making it the indispensable partner for education and research for over 100 years. Narrow mouth with a heavy tooled rim. White enamel graduations are approximate. 250 mL.