PYREX® Wide Mouth Heavy Duty Low Actinic Volumetric Flasks feature low actinic stained glass to provide 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 the PYREX® labware. The heavy duty, wide mouth accommodates pipet filling and mixing. Easy to read graduation line is sharp and permanent. Designed for microchemical work and calibrated to Class A Tolerance. Each flask features a PYREX® stopper.