Special twist-on connectors (or "wire nuts") are available for joining aluminum to copper wire, which are pre-filled with an antioxidant compound made of zinc dust in polybutene base with silicon dioxide added to the compound to abrade the wires. As of 2014 there was only one twist-on connector rated or "UL Listed" for connecting aluminum and copper branch circuit wires in the U.S., which is the Ideal no. 65 "Twister Al/Cu wire connector". These special twist-on connectors have a distinctive purple color, have been UL Listed for aluminum to copper branch circuit wire connections since 1995, and according to the manufacturer's current literature are "perfect for pig-tailing a copper conductor onto aluminum branch circuit wiring in retrofit applications". The CPSC still considers the use of twist-on connectors, including the Ideal no. 65 "Twister Al/Cu wire connector", to be a "temporary repair".