CHAMPION, COPPER PLUS SPARK PLUG. H8C
H-D #4. 14mm threaded. 12.7mm (1/2") Short reach. Used with a 21mm spark plug socket. Copper-core center electrode. Spark plug comes with the patented Ultraseal™ coated shell, to help keep the spark plug body corrosion free and better looking for a longer period of time.

Fits: > 54-56 KH; 57-85 XL