The Firestone Hy-n-Dry stopper inexpensively makes any standard taper vessel a desiccator

A pinhole in the provided plastic cap allows the assembled unit to “breathe” with temperature fluctuations through, not around, the desiccant. A warming trend or trace solvent evaporation does not produce pressure buildups that often cause the stopper to pop out. When filled with a drying agent like Drierite, a [ST] 24/40 Hy-n-Dry stopper will absorb up to one gram of water. Fabricated from borosilicate glass.

Allows sample storage for long periods, free from atmospheric moisture, even during overnight temperature changes or when refrigerating. The bottom of the stopper has a 70-100 micron sintered glass disc sealed in. To use, fill the stopper with a drying agent, cover with plastic cap (supplied), insert into any jointed vessel, boiling flask, volumetric flask, or cylinder, and you have an inexpensive desiccator.