Click here for Wookieepedia's article on the Canon version of this subject.  This article covers the Legends version of this subject. 

OnALegendsArticleGoToCanon

Polarity sinks were standard pieces of equipment installed on several models of Industrial Automaton's R-series astromech droids. They were present on R2, R3, R4 and R5-series astromech droids.[1]

Sources

Notes and references