Spectra Premium Spectra Ignition Coil C-857 Unit is designed to Original Equipment (OE) fit, form and function requirements accomplished by leveraging Spectra Premium's OE engine management systems design expertise 100% copper base in both primary and secondary windings Windings insulated by high voltage enamel coating Unit is tested for durability through long-cycle thermal shock test (-50 to 300 DegreeF), ensuring reliability against extreme vibrations Each new coil is road tested to ensure real world performance and to verify that each design meets our high standards for quality