Make labeling your plug wires simple and easy. DEIÂ's numbered wire marker sets are made from high temperature Mil Spec black heat shrink tubes. They are tough enough to handle high under hood temperatures and are easy to install. High shrink ratio of 3 to 1 allows our markers to slide over plug boot ends and still shrink tight to the wires. Sets are numbered 1 through 8 in a high visibility white ink that is oil and chemical resistant. 3-1 Shrink ratio 8-Piece Set Offers clean & professional under hood look Keep track of wires