MCS-931601 - 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. This D16 is available as MCS 9

Fitment:
750(45")/1200(74")/1340(80") Side Valve (Flatheads); 36-47 Knucklehead (61/74") (OHV) models (NU)