Flask is permanently marked with an individual serial number. Supplied with a Certificate of Graduation Accuracy. Graduation ring is blasted on the neck. Calibrated to contain and supplied with a polyethylene snap cap and a marking spot. Flasks have been carefully selected to meet the requirements for accuracy, appearance, glass quality, calibration line, and inscriptions of former NBS Circular 602. The 500mL size is suitable for determination of specific gravity of fine aggregate (ASTM C128). Designed from ASTM Specification E288, Class A serialized requirements.