BEST FOR HIGH COMPESSION MOTORS & LONG HIGH SPEED RUNNING
H-D #4, one range colder. M18 X 1.5 threaded. 1/2" (12.7mm) short reach. Used with 24mm spark plug socket. This D14 (H-D #4) is one range colder (runs less hot/removes heat faster) than the standard D16 (H-D #3) spark plug. The cooler running proporties make this D14 is better suited for high speed riding, as found in extended highway use. Spark plug is copper-core center electrode and comes with the patented Ultraseal™ coated shell, to help keep the spark plug corrosion free for a longer period of time.