Aluminized Plug Wire Sheaths are constructed from high-temperature rated glass fiber material bonded to a heat reflective aluminized material. Plug Wire Sheaths are an inexpensive alternative for protecting specific areas on both ignition wire and boot locations from damaging heat generating sources.. Plug Wire Sheathâ„¢; 3/4 in. x 6 in.; 4 Pack; Aluminized; Universal