Improve the performance of your Harley Davidson or Kawasaki with these high-quality Splitfire SF426C spark plugs. These multi-electrode spark plugs are designed to provide efficient combustion and optimal engine performance. They are compatible with a range of interchange part numbers including AGS42C, J16CR-U, RN12YC, and W8LCR, and are suitable for gasoline-fueled engines with a voltage of 12 V. Made of copper material, these spark plugs are manufactured in the United States and are not vintage parts. Upgrade your ignition system with these performance parts and enjoy a smoother ride.