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.