Ring

A ring was an item of jewellery which was placed on a finger.

Rings could be used as bio-dampers. The Tenth Doctor gave Donna Noble a bio-damper in the form of a ring so that she would be hidden from the Racnoss. (TV: The Runaway Bride) Gavin wore a bio-damper ring he inherited from his father which hid his alien origins. (TV: The Empty Planet)

John Hart was in possession of a ring that could emit a tracking signal to last 5,000 years. He threw this ring in with Jack Harkness when he was burying him. (TV: Exit Wounds)