Cool-It Plug Wire Sleeves Thermo-Tec's  double-wall construction keeps the wire and boot cooler in a high-temperature engine. Its universal size fits most boots, is easy to install and - most important - is non-flammable.  Cool-It Plug Wire Sleeves can be used in any high-temperature environment from street vehicles to motor homes. Sleeves are available in packs of 4 & 6