These narrow mouth 250mL Pyrex® Erlenmeyer flasks have low actinic stained glass that provides protection for materials sensitive to light. The protective color is an integral part of the flask, which retains the mechanical strength, chemical stability and thermal resistance of Pyrex® labware. For convenience, these flasks are graduated to show approximate capacity. These flasks have No. 27 Pyrex® ST stoppers for secure sealing. For replacement stoppers see Cat.No. 1-7650. Flaska are approximately 82 x 140mm.