"Vader, keep that away from me!"
"The injection arm is primed!
―Leia Organa and Darth Vader[src]

An injection arm or injector arm was an attachment installed on droids such as medical droids and interrogation droids. A droid limb with an hypodermic injector, it was used to inject various substances into the droids' patients or victims. Prior to an interrogation, it needed to be "primed;" it was also necessary for the subject to remain still in order to facilitate ease of use.