The Ultimate Flickering Fireplace Unit has been designed to provide the most realistic flickering fire effects available anywhere. Its features create a natural, true-to-life fireplace flicker and not the usual on/off operation. No more flashing--just a gentle realistic flicker to put warmth and glow into your fireplace and lights. The unit comes with four bulbs: three flicker and one constant. Each flicker bulb is controlled by a separate electronic circuit, creating its own independent flash rate. The supplied bulbs can be installed either in the supplied coal insert or used separately in an existing fireplace. The included bulbs are oversize to provide the maximum possible light output and are attached with screws for easy removal and replacement. They are not soldered in place. Operates from dollhouse power (either 12VAC or 12VDC) and is guaranteed not to flicker other dollhouse lights. Small circuit board size (1”W x 13 ⁄4”L x 3 ⁄4”H) allows easy concealment. Complete installation and operation instructions are included with each package. Can also be used to create a flickering Christmas tree--simply use CK1020-1 or CK1020-2 Xmas strings in lieu of the supplied bulbs for a dramatic Christmas tree display. Red replacement bulbs and amber replacement bulbs available.