The Injectors resemble bacteriophages, which are viruses that can infect and reproduce within bacteria, sometimes destroying the bacterium itself. The bottom of the machines have one large drill, surrounded by smaller ones. Thin, jointed appendages are located near the drills, presumably for walking. The upper structures sport large, red, gem-like ornaments on the top. The body of the rig itself seems to showcase a clear panel containing within it what appears to be either an organic heart or an artificial womb. These seemingly organic hearts/wombs are attached to the head and feet of the machine via red and blue tubes that resemble arteries and veins, respectively.
There's also a opening panel on the side of the base, which Gemstones can be placed inside. The drill piece digs a hole into the ground, and injects the gemstone inside, the smaller drills used to bury the gemstone inside for incubation.
Only one Injector was shown to actually operate down on Earth, which was used by Peridot to place Star Quartz into the Prime Kindergarten grounds. However, it can be assumed once emerging, Star Quartz destroyed the Injector, making it dysfunctional much like the rest of the Injectors within the kindergarten.
A much larger, customized Injector was used by Spinel after she agreed to join sides with Grogar against the Harmony Gems, revealing this particular injector was made by White Diamond purely out of boredom. This one operates differently from other injectors, made to destroy planets instead of creating Gems. The injector itself hardly got much poison into the Earth, but its legs were cut during the rematch fight with Grogar, making it collapse and brutally explode, releasing all of its poison abruptly.