Original Engine Management 4959 Distributor Cap Distributor caps are manufactured to match O.E. form, fit and function. They offer the following high-performance features: *Polypropylene, PBT, or Thermoset molding material for maximum dielectric strength and resistance to carbon-tracking Brass, aluminum, stainless, or tin-plated terminals and inserts for superior conductivity. Internal resistor to O.E. specification High-temp silicone jacketed wires Silicone coil &amp; plug boots &amp; components