Round bottom and long neck 30 mL size has square-cut mouth for multiple micro digestions; mouths of larger sizes are tooled for uniform rubber stopper fit. 30 mL flask conforms with ASTM Standard E 147 for microchemical apparatus; 100 mL through 800 mL flasks can be used in ASTM E 258 procedure.

Reinforced bead at top 300 mL and larger sizes have tooled necks 10 and 30 mL sizes are designed from ASTM Specification E 147; 100 mL through 800 mL sizes are designed from ASTM Specification E 1377, Type 1 requirements.