A special glass vessel used for holding or measuring out a precise volume of liquid to a high level of accuracy. The vessel has a pear-shaped body with a long, tall neck coming out of the top. At a certain point on the neck is etched a calibration mark. When the flask is filled with liquid such that the meniscus of the liquid is at the calibration mark, the volume of the liquid will be known to a high level of accuracy.

Volumetric flasks are manufactured in many volumes, including 10.00 mL, 25.00 mL, 100.00 mL, 250.00 mL, and 500.00 mL. A 250 mL beaker can only measure out liquid to ± 5 mL, but a 250.00 mL volumetric flask can measure out liquid to ± 0.12 mL. These flasks are always used in the preparation of standard solutions.