ACCEL Brute Thunder HEI Super-Coils are engineered to be the highest-output HEI in-cap ignition coils available and are a direct performance replacement for stock units. These coils feature highly specialized silicone-magnetic steel cores that, together with their optimized winding resistance and turns ratios, deliver 10-15 percent more energy than Original Equipment Manufacturer coils. ACCEL Brute Thunder HEI Super-Coils are compatible with both original HEI ignition systems and later model computer-controlled systems. Specialized high-temperature epoxy resists shock and vibration and still increases thermal conductivity. Mounting screws and a ground strap, silicone coil gasket, and low-Ohm contact brush/spring are included.