For use with low-impedance injectors. Compatible with injectors with impedance between 2 and 6 Ohms. Please contact us if you are planning on using injectors with an impedance of less than 2 ohms. Includes set of 4 x 4.7ohm 25w resistors mounted to a heatsink. These are also sold in a set of 6. Note that injector ballast resistors get quite hot at high injector duty cycles. These should stay mounted on the supplied heat sink and be bolted to the chassis.