These Pyrex® Vista™ volumetric flasks provide precise volume measurement. The necks are tooled for ST glass stoppers. The graduation line is sharp and permanent and large blue block letters make the inscription easy to read. The 1mL and 2mL sizes are test tube shaped. These 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.