Absolutely required for points-triggered ignitions equipped with coils that do not feature a built-in resistor such as Moroso PlasmaPulse 72380, Accel Super Coil 140001, Super Stock High Vibration 8140HV, Racing Coils 140108, 140205 and 140305; Crane PS20 and PS40, Jacobs's 380672T and MSD Blaster 2 - 8200, 8202 and 8203, Baster 3 - 8223 Ceramic base supports resistor to eliminate the possibility of electrical shorts and to dissipate heat Includes built-in mounting boss; must be mounted to firewall or other metallic surface to further dissipate heat 1/4" spade terminals facilitate wiring to battery side of the coil