Internal Ceramic Beads - Tumbles gas to create a dancing flame every time Millivolt Valve - Includes an on/off switch For Use with - Empire "LS" log sets of the same size Burner Size - 18-Inch; Fuel Type - Natural Gas The White Mountain Hearth VFSR18NAT Ventless Slope Glaze Burner with Millivolt Valve, 18-Inches, Natural Gas raises the standard for flame presence while integrated ceramic beads tumble the gas to form an ultra-realistic fire. The Vent-Free Slope Glaze Burner can reach up to 38,000 BTU while the Millivolt Safety Valve includes an on/off switch to allow easy control over your flame presence. This burner requires an Empire LS log set in a matching size for optimal fireplace performance. Empire's focus on high quality construction and performance ensures a burner system that you will be able to enjoy for years to come.