The volumetric flask
A volumetric flask is a pear-shaped container with a flat bottom and narrow neck.
It is a gauged container: it allows you to measure a very precise volume. It is the volume contained in the vial that is accurate - so it is type In glassware.
The gauge mark is indicated at the neck of the flask. There are several sizes of flasks depending on the volume (usually 20 ml to 1 L). Each flask contains a precise fixed volume.
Generally a volumetric flask is made of glass, but there are also plastic ones. There are short-necked and long-necked flasks for the same volume.
A volumetric flask is used to prepare solutions of precise concentrations: initial stock solution (by dissolution of a solid, or by dilution of a liquid), or daughter solutions after dilution of the stock solution.
For this it is necessary to fill the flask up to the mark: the bottom of the meniscus must be visually at the level of the mark. It is important to shake the solution halfway through, i.e. before filling up the flask.
read the sheet on How to prepare solutions and dilutions