The Sniper EFI Coil Driver Module is designed to be used in place of a capacitive discharge box. This coil driver is utilized to amplify the energy transferred to your spark plug, promoting complete combustion in the cylinder! Features: Compact size allows for easy installation without cluttering up your engine bay! Labeled wires take the stress out of your wiring installation Requires Canister Style Ignition Coil The 556-150 is the Sniper EFI Ignition coil driver module. It can be used in the place of a CD box in installations that need something to drive a coil. If you search the below document for the term "coil driver" you will find several sections of the instructions with information regarding this component. Basically , the Driver essentially replaces an MSD box with regard to wiring and functionality. That being said, the coil driver shouldn't be used on a higher horsepower applications, but rather for anything street horsepower numbers under 500hp.