ACCEL Y2418P Platinum Spark Plug - Pack of 2 Fit Harley Davidson Twin Cam with .40" gap. Manufactured from the best materials available. Premium quality platinum tip is more durable which will maintain the proper gap much longer By using the proper spark plug gap requires less voltage to fire so you will have fewer misfires for long periods of use. Pure copper center electrode reduces fouling. Easier starting, improved fuel economy, Smooth idling and quicker acceleration