Microburst Flask

A Microburst Flask is an unussual ammo type for Plasma weapons.

Filled with much higher concentrations of heavy ions, Microburst flasks allow a plasma weapon to fire smaller but denser bursts at farther ranges and with greater armour penetration. Microburst plasmas are cooler, however, but many users prefer it this way, given the normal thermal temperament of the weapon.

The end result is that damage output is decreased and cannot be fire in Maximal/Overcharge mode, in exchange for higher penetration and a slight increase in range.

Speculation
The Microburst Flask may be the method in which the Tau, and possibly other races in the galaxy as well, use in their plasma weapons to increase the reliability of their Plasma weapons when compared to the Imperium.