The accuracy of standard glass flasks combined with the break resistance of plastic. Gravimetrically calibrated individually TC/TD at 20?C. Printing is durable; won?t wear off. Guaranteed to meet the class B accuracy requirements of ASTM E288 and ISO Standard 384. No meniscus to confuse readings. Oval marking spot. #77089 has additional line at 203-ml level for BOD and DO determinations. Can be autoclaved, but accuracy will be affected. Before autoclaving, set closure on top of the container without engaging the threads.