These PYREX 5mL volumetric flasks provide improved lab convenience, broad selection and precise volume measurement. The strength of these flasks has been increased appreciably through machine-blown bodies to which are sealed heavy-tubing necks tooled for No. 8 Standard Taper glass stoppers. The graduation line is sharp and permanent and large white block letters make the inscription easy to read. These Class A volumetric flasks have been manufactured to Class A tolerances as established by ASTM E- 694 for volumetric ware, ASTM E-542 for calibration of volumetric ware and ASTM E-288 for volumetric flasks.