Mend or extend aluminum wire often found in older buildings. This wire isn’t recommended for new wiring, since it’s more likely to overheat than copper when conducting electricity. However, it’s safer to maintain existing aluminum wire with aluminum rather than mixing materials. Building wire is also known as branch circuit wire.

This wire has an outer layer of nylon insulation that won't degrade from oil and water. It’s designed to be pulled through conduit without pulling lubricants. THHN and THWN-2 designated, this wire can be used in damp places.

Also known as fixture whips, this cable has locknuts and fittings attached to the metal armor to secure to a knockout. The armor acts as conduit to protect the THHN building wires. It has 6" long wire leads for hardwiring to an existing electrical system, and is often used to connect light fixtures.

Also known as AC cable, this cable has an uninsulated aluminum ground wire that's in constant contact with the aluminum armor, so it can be used for bonding and grounding. The uninsulated ground wire is not counted in the number of wires. The armor acts as conduit to protect the THHN building wires. It's often used along the exterior of walls to carry power to outlet boxes. All are flame rated VW-1 to meet requirements for preventing the spread of flames based on a timed test with vertically suspended material.