A volumetric flask is a pear-shaped, flat-bottomed volumetric flask with a narrow neck and a ground glass stopper. It has a graduation mark on the neck indicating that at the specified temperature, when the concave meniscus of the liquid is tangent to the graduation mark on the neck of the flask, the volume of the solution is exactly equal to the volume marked on the flask. Volumetric flasks are marked with: temperature, volume, and graduation marks.