Nalgene™ polypropylene flasks offer the accuracy of standard glass flasks combined with the break resistance of plastic. With polypropylene screw cap. Graduated and leakproof. Gravimetrically calibrated individually TC/TD at 20°C. Printing is durable and 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. Cat.No. 7-4000-0200 has additional line at 203mL 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.