Works with the Iron Man Mark IV Arc Reactor: https://www.shapeways.com/model/1654421/iron-man-mark-iv-arc-reactor-1-of-2-parts.html?li=aeTabs. This is a light diffuser box. Just wire some LEDs into the box and place behind the Arc Reactor. This will help evenly give off light from behind your Arc Reactor. Please take measurements before ordering to be sure this will work for your suit, your Arc Reactor chest cavity may not be the same size as others.