Make labeling your spark plug wires simple and easy. DEI'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 temps and are simple to install. The high shrink ratio of 3-to-1 allows these markers to slide over plug boot ends and still shrink tight to the wires. Sets are numbered 1 thru 8 in a high visibility white ink that is oil and chemical resistant.