Sonic droids were used as infantry by the Grigorian military. Their appearance was strange to say the least, and appeared to be modelled after several different droids. Their appearances were very similar to smaller versions of the SD-6 Hulk infantry droid but had some important and lesser differences. The standard claws of hulk droids had been replaced with more capable hands for carrying blaster rifles or sonic rifles, their heads were based on the hunter-killer droids with one green sensor, they were considerably much more intelligent and finally they were color-coded to signify rank. Green would mean standard, blue would be bodyguard and red would mean commander.