Kimax® flat-bottom flask is permanently marked with an individual serial number and is supplied with a Certificate of Graduation Accuracy. Graduation ring is blasted on the neck. Flask is calibrated to contain. Supplied with a marking spot and a ST ground glass stopper. These flasks have been carefully selected to meet the requirements for accuracy, appearance, glass quality, calibration line, and inscriptions of former NBS Circular 602. Designed from ASTM Specification E288, Class A serialized requirements.