NGK TR55 Spark Plugs (set of 4), V-Power spark plugs are a patented design by NGK to improve ignitability and reduce quenching. Ignitability is improved by the V-groove cut in the center electrode parallel to the ground electrode, this directs the spark to to the edge of the center electrode thus exposing it to more of the air/fuel mixture. Quenching is reduced in much the same manner, drawing the spark to the edge of the center and ground electrodes reduces the surface area available to quench the spark. Shipping is not included.