Choosing a sound firebox is the first step in setting up a gas fireplace system in your home. Depending on where you want to place that firebox and the structural makeup of the space, you may need a vent-free firebox. The black box by Heat Master comes with a realistic masonry and brick liner for a traditional fireplace look. It is prewired with Thermo-disc and features a pre-mounted blower to make installation easier. With gas access on either side of the box, there is no need to reconfigure existing gas lines. Both the 36 inch and the 42 inch provide optimal viewing space.