Improves starting! Up to 15% increase in power

The Pertronix Flame-Thrower Coils feature a square body or round body (depending on application) and are an optimized coil design for 15% more spark energy. They are a direct fit replacement. •15% more available spark energy burns all fuel in the cylinders for more power, quicker, starting, and improved mileage. •Designed to perfectly fit the factory mounting holes for direct OE replacement fit. •OEM style factory connectors plug directly into factory wiring harness and lock directly into place. •Where applicable, high temperature boots secure the spark plug insulating the high voltage ensuring all energy is delivered to the spark plug. •High temperature epoxy insulates the coil windings to prevent voltage breakdown in high temperatures. •PRT0811 replacement for GM Part#s 12558693/19355500. •PRT0851 replacement for GM Part#s 12619161/12669351. •PRT0861 replacement for GM Part#s 12699383/12621750/12658183.