NGK 4291 V-Power Zfr6f-11 Improved performance over OEM and Standard plugs for high performance operation with a 30,000 mile service life. Advanced V-groove design and high performance Nickel electrode enhances spark development. Economical performance plug for older vehicles. Precision laser-welded electrode construction. Trivalent Metal Plating has superior anti-corrosion and anti-seizing properties.