Used to make electrical connectors that are exposed to air and corrosive conditions, this 99.99% pure gold wire stays highly conductive where other conductors would fail. It also has a high melting point, low thermal resistance, and won’t oxidize, so it’s good for making parts that remain accurate in extreme environments. Compared to platinum, gold is more conductive but has a lower melting point. It’s often used to make O-rings, even for high-vacuum applications, because it’s soft enough to form a good seal when pressed between two flanges, yet won’t damage the flanges so you can reuse them.