It is not a voltage stabilizer, it is a volt stabilization technique used to get proper voltage strength. U just have to ground the battery negative terminal to 3 different positions in the engine bay with a 4 gauge or 8 gauge wire, 4 gauge is recommended. One wire to the body (Color scratched), one to the engine and one with throttle body or any part in the engine.
Without this technique u will get approax 15v on idle and almost 16v when u will rev it. Do check the voltage before and after this grounding and u will see the difference.