The labels on the outer sheathing of NM cable indicate the size, or gauge, of the individual conducting wires, the wire material, the number of wires contained inside the cable, the maximum voltage rating, and whether there is a ground wire present. The wire size and number of wires are indicated with numbers.

Vinyl labels are popular because they resist moisture, smudging, and tearing. For more durable options, polyester or polyolefin materials may be used.

There are 3 main types of wire and cable markers that are used by electricians, technicians and network installers alike: Heat Shrink Labels, Self Laminating Wire Labels and Wire/Cable Tags.