Selenium was a substance that could be used in the composition of drives of BB-series astromech droids. When Kylo Ren pressed Rey for details about the droid known as BB-8, she listed technical specifications such as a selenium drive, evading the real focus of Ren's inquiry: the map to Luke Skywalker that the droid contained.
- Star Wars: The Force Awakens: The Visual Dictionary
- Star Wars: The Complete Visual Dictionary, New Edition