The 39 inch Pre-cast Masonry Firebox Kit - Wood Burning will bring the family together for a night around the fire. Pre-cast from modular concrete at half the cost, this firebox is not only lighter, but also up to 70% tougher than the competition, with a refractory strength of 3500 PSI. This unit transforms your hearth from a basic metal firebox to an artistic stonework creation, and because it weighs less than traditional brick fireplaces, it can be installed on any floor of the home without the need for additional reinforcement. The base is pre-drilled to make rebar installation a breeze, and the 50-pound bucket of dry mortar that comes with the kit has everything you'll need to finish the job. The entire firebox can be completed in less than two hours, as opposed to a traditional installation that can take up to three weeks. The knock-out is easily mortared off with the accompanying concrete plug for those who choose to keep their fireplace wood burning only. No on-site drilling will be required for individuals who want the convenience of a propane or natural gas fuel line. Although glass doors are compatible with this firebox, they should not be left closed when a fire is burning. Additional downdraft and fire safety can also be achieved with the use of spark arrestors and chimney caps. The unit is pre-assembled and ready to use, with a fuel line knock-out that you can put on either side of the firebox. Please refer to the PDF charts supplied for all relevant measurements. All elements and components are proudly made and distributed in the United States, and they meet UL 127 and UL 103 chimney standards. This firebox has an ICC-ES rating.