Sure Heat RS18VFTNG Vent Free Dual Burner Log Set for Natural Gas Fueled Fireplace, 18", Riverside Oak Nine highly detailed, hand painted ceramic logs traditionally stacked on a tiered grate realistically recreate the look of a mature fire in your fireplace CSA approved heating appliance will heat 1200-1500 square feet with 99.9-percent efficiency Fits all fireplaces with minimum dimensions of 28-inch front width; 15-inch depth; and 21-inch back width Thermostatically controlled to maintain a consistent room temperature 100-percent carbon monoxide and oxygen depletion safe.