Assimilation tubules are a technology used by the Borg to deliver nanoprobes to prospective drones and to allow nanoprobes to create interfaces with technology to allow a drone direct control.
Injection tubules are normally found in the hands of drones. (TNG movie: Star Trek: First Contact)
In 2376, the crew of the USS Defiant discovered that Borg technology such as assimilation tubules can survive the death of the drone under certain circumstances. This information allowed Elias Vaughn to stop the assimilated Ruriko Tenmei from assimilating Prynn Tenmei. (DS9 - Mission Gamma novel: Lesser Evil)