These Class A volumetric flasks are calibrated "To Contain" and have marking areas flasks. The 1-mL and 2-mL flasks are of a test tube shape, all other sizes are conventional flasks. The 5-mL and larger flasks meet Class A ASTM Specification E288 unserialized specifications. The 1- and 2-mL sizes are test tube-shaped and are calibrated to E237 tolerances.