Cyber-helmet

Cyber-helmet was a term used, by the Sixth Doctor at least, to refer to the head of a Cyberman. He kept one such Cyber-helmet in his C chest. (AUDIO: The Carrionite Curse)

In the case of the Cybermen from Pete's World, the brain their helmets contained was the sole organic component that remained in a Cyberman. (TV: Rise of the Cybermen/The Age of Steel)

Lesser Cyberslaves appeared as metallic humanoids with Cyber-helmets. (GAME: Blood of the Cybermen)

Despite being detached from its body, the helmet of a damaged and automated Cyberman suit made a failed attempt to replace its expired organic components by assimilating Amy Pond. To that end, the Cyber-helmet opened up and empited itself of a humanoid skull by closing back again and firing a dart at Amy's neck, which rendered her unconscious. (TV: The Pandorica Opens)

Having been stripped of its organic components, a Cyber-helmet named Handles was claimed by the Eleventh Doctor at the Maldovar Market. Having a cybernetic mind of his own, Handles would serve as a companion just prior to and during the early centuries of the Siege of Trenzalore. (TV: The Time of the Doctor)