Duluth Forge Vented Natural Fireplace Set-24 in, 55,000 BTU, Heartland Gas logs, 24, Oak Natural Gas operation Liquid Propane conversion kit available; Model NVDWA1 1 bag of Glowing Embers and Vermiculite each Included Minimum Firebox Size Required: 18 H x 24 W in front (18 W at rear) x 15 D Designed for Indoor Use Only