Very often it becomes important to save, store, or transport important SEM, TEM, LM or other kinds of samples (e.g. LC ""liquid chromatography"" standards) under an inert atmosphere. The SPI-Dry Sample Preserver Capsules are designed for purging with an inert gas so that the samples are not necessarily stored under vacuum, but rather they are stored under a positive pressure of the pure inert gas. A vacuum could be used for faster purging by evacuating and then purging and backfilling to a positive pressure. But what distinguishes these Capsules from other storage systems is the ability to store long term under positive pressure.
Of course, if desired, the SPI-Dry Sample Preserver Capsules could be used as a vacuum storage device but that would not be the best utilization of this product.
Putting it another way, the SPI-Dry Sample Preserver Capsules are specialized containers that enable one to replace the reactive atmospheric air typically present in the container with an inert gas.