Zirkonian Flares let off light similar to earthen fireworks, they are used to call Zirkonian invasion ships. In order for the light of the flares to be seen by the Zirkonian invaders the flares need to be supersized which can be done with the use of the Sizematron.
They are used once in the movie by Skip after he enters the Sizematron he places the flares and activates them, successfully calling the Zirkonian invaders.