Delphi GN10638 Pencil Coil Delphi uses winding process techniques to control the length of wire between adjacent windings. Thats important because more length results in greater voltage differences, which in turn create more pressure that could break down the insulation and wire coating. Delphi's ignition coils are engineered to Original Equipment specifications Delphi's ignition coils are designed with proven materials, such as high quality wires and wire coating that resists the cracks, pin holes and imperfections that most often lead to failure issues Epoxy vacuum techniques reduce air bubbles in the epoxy, because having fewer air bubbles increases the epoxy's insulation quality and reduces the chances of energy punch-through failures Delphi's coils are designed and endurance tested to resist the common stresses that cause failure