This 250mL Erlenmeyer flask is made from heavy-duty borosilicate 3.3 amber glass for storing light-sensitive chemicals. The flask features uniform wall thickness ideal for heating, a reinforced rim for impact protection, and easy-to-read white enamel graduations every 50mL. The flask measures 5.7 inches tall and 3.3 inches in diameter with a 34mm narrow neck opening. Conforms with DIN ISO 1773 standards for narrow neck conical flasks. Microwavable and autoclavable with superior chemical resistance and thermal shock resistance.