Pyrex® microvolumetric flasks are calibrated to Class A tolerances. Individually serialized and supplied with a Certificate of Identification and Capacity. They are designed for microchemical work in accordance with the recommendations of the Committee of Microchemical Apparatus, Analytical Division of the A.C.S. To improve the stability of this small flask, a hexagonal base, similar to those on all cylinders, has been added. Uses a ST Pyrex® stopper. For replacement stoppers, see Cat.No. 1-7650. The graduation line is sharp and permanent, with easy to read white markings. Reference: ASTM E-237.