Borosil® Wide Mouth Class A Volumetric Flasks are individually calibrated by automatic, laser-controlled calibration equipment. Supplied with standard taper glass stoppers. Flask are Comply with ASTM E288, ClassA. 20mL option is not covered in ASTM. 5mL, 10mL, and 20mL options have a trapezoidal shape for improved stability. Available from 5mL to 1L. Larger Class A Flasks available in Product Family 5645. In collaboration with Borosil Glass Works, Foxx Life Sciences is proud to bring the outstanding quality of Borosil® Type 3.3 Borosilicate glassware to North America for the first time. Manufactured from the same USP Type 1 borosilicate glass that North American scientists have come to trust, Borosil® Laboratory Glassware offers unparalleled mechanical strength, clarity, and reliability at competitive prices. And thanks to a unique annealing process, Borosil® Glassware is stress-free and incredibly resistant to thermal shock.