Amberized glass provides protection to light sensitive solutions. Allowing less than 1% transmission below 400nm and 5% from 400-600nm. Wide mouth design facilitates mixing, pipette access, sampling and filling. Unique Flat Bottom Interior permits the use of a standard stir bar. Large permanent white letters make the capacity clearly visible. Flasks are calibrated "To Contain" at Class A tolerances, per ASTM E288 specifications. Supplied with a glass stopper.